I suspect that most people who believe in these “commonly referred to as mythological” creatures, do so for a myriad of reasons. In my opinion, the reasons for believing in them far outnumber and outweigh other folk's reasons for not believing in them.
Here are a few reasons why I, and a rapidly growing number of people, believe Bigfoot exists….
Footprints are an excellent and dependable bit of evidence for the presence of any walking animal. In fact, footprints are considered by all mainstream scientific authorities as an effective and accurate means of determining population in a given area. However, since mainstream science doesn't want to even entertain the possibility that Bigfoot exists, they've disqualified footprints as evidence of their existence.
Every day across the USA and Canada, Sasquatch footprints are found by both those looking for them, and by random hikers and outdoorsy people enjoying nature. Now when I say they are finding footprints, I'm not talking about mere outlines of big barefoot feet placed one after another on a path somewhere. I'm saying that dynamically placed, anatomically accurate, scientifically and mechanically actual footprints are being left behind by living breathing walking bipedal creatures. They indicate a flexible foot of a creature that weighs sometimes up to 600-800 lbs. The toes are in a different position in every subsequent print, they demonstrate accurate bone structure required for a creature of that size, and they present with dermal pressure ridges. People know about these things now, but 60 yrs ago when the first tracks were cast, nobody, not even many anthropologists, had any in depth technical knowledge of what tiny details are important when considered as evidence for a previously unknown hominid.
Microscopic details found on prints cast 50 and 60 years ago have numerous exact same aspects as prints found today on the opposite end of the country. These facts lead me to believe that most footprints found are not the product of a hoax. For a hoax to be perpetuated in this area, literally hundreds of extremely knowledgeable and skilled craftsmen who all really desire to create an ongoing flawless hoax, would have to all be in cahoots with similarly skilled craftsmen and scientists across the country over the past 60 yrs. In my opinion, the odds of that being likely are pretty close to zero.
Any police officer or psychologist will tell you that the skills of accurate observation in the common person are questionable at best. This is especially the case when the witness is under physical or emotional duress. Ask an armed robbery victim what color shirt the criminal was wearing, and they are likely to tell you something totally different than what another witness says. This fact is used as the main reason mainstream science tends to disregard all Bigfoot sightings as mistaken identity. Whether it was a bear, another person, or a tree stump, they feel that even those who had up close face to face encounters with these huge terrifying creatures were incorrect when they identify what they saw 10 feet away as an 8ft hairy manlike apelike beast who growled and bared their teeth at them. It had to be a bear or a clump of branches that did all that then turned and walked away into the woods behind them.
Well, I don't buy it. While I have no doubt that mistaken identity occurs every day, I truly do not believe that every witness account is incorrect. Maybe one or two out of ten, but I believe that the vast majority of those who say they saw one of these creatures, saw one of these creatures. The fact that many eyewitnesses have spent a lifetime exploring nature, whether hunting or fishing or hiking or camping, and have encountered the myriad of different flora and fauna out there on numerous occasions, is proof enough in my book that they are educated enough on what all is out there in their favorite patch of woods to know that what they saw 30 feet away digging for grubs in a rotten log, then stood up and growled and stomped off into a thorny plum thicket was not a stump or a bear or a guy in a hoodie.
Witnesses in new york state report very similar creature details as witnesses in tennessee. Witnesses in mississippi report very similar creature looks and behavior as witnesses in east texas. In literally every state in the union these creatures are continuously spotted, except of course, in Hawaii. If indeed all Bigfoot sightings were the product of a hoax or mistaken identity, why do we not see Bigfoot sightings in Hawaii? Are people in Hawaii less prone to pulling pranks on others, and do those who live in Hawaii somehow magically transform into uber accurate observers? Who knows? It does give you food for thought tho.
…There is room for them to exist
Even tho these creatures can and often do inhabit areas close to where Humans live or visit, their most favored domain is most likely where they can be alone, unbothered by pesky Humans and their boom sticks and chain saws. Most people aren't aware that there are still ranges of wilderness scattered throughout the USA and Canada that either have never been visited by Humans, or are only visited by Humans every few dozen years. Steep cliffs, thick thorny fields of overgrown brush, swampy marshy, snakey wetlands, high rocky mountaintops, thick forests that go on and on for hundreds of square miles, are all places that Humans tend to avoid, and THAT, in my opinion, is the key to this species remaining hidden and unresearched, compared to other typically hidden animals.
Regardless of how many scientists claim that any given area could not support these creatures food-wise, their vastly varied suspected diet would enable most areas to support one or more individuals over the course of the 4 seasons. While a particular spot may not be fertile enough grounds for the entire year, an adjacent valley or mountainside may provide more than enough plant and animal life to give ample sustenance. When discussing bigfoot migration possibilities, most researchers I've seen offer an opinion feel that while the creature most likely doesn't migrate long distances from season to season, their probable permanent home range of 30-100 miles offers plenty of variation in plant and animal life, as well as Human supplied snacks, to sustain a small group of wandering creatures.
By Human supplied snacks, I'm referring to pet and livestock feed, pets and livestock themselves, food discarded in garbage, back yard gardens and farming acreages. There are numerous stories out there that document the skilled scavenging techniques these creatures exhibit around homes and other Human settlements. That’s not even mentioning the scads of folks purposefully feeding these animals in habituation sites across our nation.
The three broad reasons I've listed above are just a sample of why I believe these creatures exist. I'm betting that if I laid out all the reasons I believe in Bigfoot, it would result in 8 or 10 more paragraphs.
While I have no idea if the majority of bigfoot believers out there will completely agree with my reasons for believing Bigfoot exists, I suspect that their lists of reasons wouldn't be too awfully different. Its certainly an interesting subject with a vast variety of opinions on every aspect of its existence. For every opinion out there on some detail, there is going to be a differing opinion opposing it. Until we either capture or kill one and make it available for mainstream study, it will continue to be the hugely debatable topic we find it to be today.