Much of the developing world still squats, not just over their toilet, but also for sitting/resting in open spaces. I'd bet excessive knee stress is a "Western" thing, caused by poor joint flexibility and poor core strength.
A lot of the difference is ankle mobility, westerners don’t sit in the resting squat position often and their ankle joints have less range of motion as a result.
Many westerner’s heel will lift off the ground attempting an Asian/Slavic squat.
Which puts a lot more stress on the knee joint. It's also hip mobility that causes this, people and unwilling or unable to press there abdomen against there thigh, which is much more supportive and helps get into a proper squat.
Also, as a person who grew up in "developing world" (though by now thoroughly "developed," i.e. become a part of EU), how are you imagining the world? That people don't have chairs? Just because I might squat while eating on a camping trip to a forest doesn't mean I don't know what a table looks like. Most of that legendary squatting happens in situations a westerner would just either stand or sit on the ground.
Where did I say any of that? Of course people sit in chairs, when they're available. But, when they aren't, people in many parts of the world will squat (vs Westerners who remain standing, or sit on the ground).
That amount of squatting will help you about as much as walking to your nearest bus stop every day. It's really not that much.
The image westerners have comes from a shock of seeing anyone squatting ever, not from how much the "slavs" actually squat.
It's not that squatting, in general, is helpful. It's that if you don't squat, you lose the ability to squat comfortably. I was initially responding to a comment about squatting blowing out knees, which doesn't seem to be a problem in regions where adults continue to squat some of the time.
