It’s an old cliché, but like most clichés, it’s based on truth: cats easily climb up a tree but often can’t climb down. Hence we have all the old jokes about calling the fire department to get the pitifully meowing cat down from the tree. Why can’t they climb down by themselves? After all, squirrels do it with ease.
The problem with climbing down is that cats, like squirrels, want to do it headfirst, in order to see what’s ahead of it. But while a squirrel’s claws are perfect for moving headfirst down a tree trunk, a cat’s aren’t. The cat wants to go down headfirst, senses he can’t, so stays where he is, and makes a lot of noise until rescued.