Nobody's forcing bigfoot to do anything, but we see them in places we assume they normally wouldn't be. Ergo, assumption that they keep to the forest of necessity is questionable.
Heck, they didn't just crop up in 1959. They've been around for millennia, and for millennia we have competed with them for prime habitat, sometimes violently if certain lore is indicative. There have even been times when we deforested far more of the continent than is now deforested.
We haven't done them in yet, and I don't think we're about to.