I don't think you realize how big the west is, and how unpopulated.
They have the intellect to bury their dead; after all, no bones of these elusive creatures have ever been found? PLEASE!
I have been in the Rockies (actively in the back country) most of my life. I have never seen the bones of a cat, or a wolf, and only twice found the bones of a bear... While deer and elk bones can occasionally be found, even that is fairly rare - Porcupines eat the bones unless they are not found until the bones are dried out. A lack of bones in the mountains means nothing.
As an avid hunter, I have hunted in Montana, North Dakota, several states that include the Rockies. I have hunted in Alaska and NW Canada. I know Grizzly bones when I see them.
Although I don’t hunt bear, I hunt in bear country and am familiar with bear bones. They do die, after all.
Also in Africa were stories of elephants that live in forests (the forest elephant). The more common African Savannah elephant was know n for centuries, but stories of elephants in forests were taken by zoologists as impossible (the natives must have been high). What they didn't know is that elephants have a very soft pad under their feet, and can veritably walk in undergrowth while making very little noise. It is almost eerie.
Anyways, Sasquatch is probably imagination only. However lack of photographic evidence or bones is not proof positive 'something' is not there. It is extremely hard to find the remains of wild animals in any wilderness. Even a domestic cat (unless immediately killed by a car) will not normally be found.