Some of us call that the "turtle position" because that's exactly what they look like
I wish I knew the answer to your question; many of us (all women) have asked the same thing.
We have come to the conclusion they probably have lousy balance and that's the only way they can balance themselves but that's just one of many very unsavory theories "we women" (that's the same as the "you people") have come up with - lol lol
If any of the men would like to chime in on this, "we women" would be more than happy to hear your reasoning behind that gawrsh-awful-you-need-shot-for-sitting-like-on-a-horse position
EDITED TO ADD: Hmmm, I like the word "vulture" too. How about "the vulture head sitting in turtle position!" :) :) :)