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.
I stopped sitting on toilets about 14 years ago after a camping trip when I realized how much I preferred squatting. I will never go back unless forced to due to injury.
So what toilet setup do you use most frequently? In the western world, all the toilets are the sitting type, as opposed to the squat-type ones commonly found in India and elsewhere.
I just lift up the toilet seat and squat over the bowl. It's only tricky on taller toilets but normally works perfectly fine. In fact, using public toilets it feels a little more hygienic as you don't actually have to touch the toilet seat or bowl.
I believe it's part of the reason my upper leg muscles have remained strong even when work has put a halt on exercise for longer periods of time.
I would be open about this if asked but never bring it up unsolicited in conversation as in the past I have found it regarded as outright bizarre.
Even if you squat over the bowl — that’s not a full squat... I’m quite familiar with this maneuver from a lifetime of squatting over public toilets to pee. Using a squat tube potty is a much more natural squat position.
Look into a Squatty Potty. An extension that is basically a stool to help you raise your feet and knees into a more squatted position to help defecate into the toilet. Or just bring a wide stool to the toilet with you that raises the same.
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.