It's because we are supposed to be really good at squatting, but modern life just doesn't require it.
The biggest difference is not squatting to use the toilet. Until modern toilets, humans squat without sitting to poop. More sitting = less squatting, which leads to not squatting to pick up things since our muscles are underdeveloped.
The biggest difference is not squatting to use the toilet. Until modern toilets, humans squat without sitting to poop. More sitting = less squatting, which leads to not squatting to pick up things since our muscles are underdeveloped.