Why does an opossum sleep hanging upside down by its tail?

The opossum's tail is prehensile: it is well adapted to grasping and
holding on to things.

The opossum's tail enables it to hang on to tree limbs, hang on to their
young, and sometimes they do hang from their tail (along with one or
more paws) when they are eating, reaching for something, grooming their
young, etc. The fact is, an opossum does *not* sleep hanging upside
down by their tails, and drawings of them doing so are inaccurate. They
sleep on top of limbs, in crevices, or in recesses just like other
arboreal animals.