Human hair growth

Why is it that the hair on our heads (and beards, for men) will continue to grow indefinitely, but all the other hair on our bodies reaches a specific length and stops growing and/or falls out? And why aren’t there any other animals who have this occurrence?

Or is there actually a maximum for this hair as well, but it’s either cut or falls out before reaching that length?

OK, sorry I didn’t check there first.

But the phenomenon of scalp and beard growth must have evolved after we became smart enough to cut it before we tripped over it.

Maybe that’s why other animals haven’t evolved long hair: they couldn’t keep it at a safe length, so it impaired their longevity.

I haven’t had a haircut in fifteen years, but mine barely reaches to my shoulders. It’s never grown any longer than that.
[sub]Wait…that sounds like MPSIMS material…[/sub]