I think we're simply talking past each other at this point. Your comments are predicated on the fact that you have never seen one and are skeptical about there existence. That's ok by me.
My comments are predicated on direct observation of more than one individual. I don't believe they exist, I know that they do. I understand that this is insufficient proof for you and that's ok by me too. I do hope that you one day have the opportunity to see one. You would enjoy it under the right circumstances.
The theory I keep going back to is that they are, in part, what they are because they have adapted to live in a world we dominate. There must have been conflict at regular intervals in the past over prime resources. A bigfoot clan living near a herding or agrarian culture would have been a menace to survival. Look at one of the primary themes from the Carter Farm account. They kept consuming the food - the goats, the cattle, other livestock, and much of the food they grew. They came to expect Grandpa Carter to feed them. When they didn't get the food they wanted, it caused conflict. Grandpa Carter let them take what they wanted most of the time. I doubt every human group subject to poaching by a group of bigfoot was so understanding. More likely, they ganged up on them and chased them out of the area, or at least tried. More likely this was the standard response. I figure they've only been relatively unmolested since people started telling us that they don't exist.
Now there's an amusing thought. We exert force against them until their numbers dwindle. They become so scarce that we put them out of mind. After a time they resurge until new reports start coming in, but we're told that they don't exist, so they continue to resurge unmolested. Finally, someone wakes up and says "Gee, look at all the bigfoot." Then it gets interesting.