This question gets asked fairly often by people who don't spend much time in the woods. It's uncommon to find physical remains of any animal in a wilderness setting, even if it's something really common, such as deer; it takes a very short time for carrion feeders of various kinds to reduce remains to invisibility. In this case, if the sasquatch exists as a biological animal, we're talking about small relict populations of a rare, nocturnal, and highly intelligent animal that avoids areas frequented by human beings.

Meanwhile people have found a great many tracks, feces, and hair samples. Scientists refuse to look at them. The unwritten law of the scientific community -- "no one but a tenured academic is allowed to discover anything" -- is just as powerful a force now as it was when continental drift was dismissed as crackpot pseudoscience.