Yes, they come down eventually, but often get seriously or fatally injured in the process. They are capable of getting up (usually being chased up) into places they can’t get down from safely, because their claws allow them to climb vertical tree trunks, but not to stabilize themselves on the way back down the same trunk. By the time they’ve waited a few days, they’re weak from hunger and dehydration (and in some cases, may already be irreversibly on the way to the often deadly hepatic lipidosis), possibly with frostbitten paws in winter, and are very poorly equipped to brace themselves in a hard landing. A cat that breaks its spine or pelvis when falling out of a tree doesn’t end up as a “cat skeleton in a tree”, but ends up dead anyway (hopefully having been found quickly and taken to a vet for euthanasia, but depending on the location, it may die slowly and in pain without being found).
I had a cat that got chased up the telephone pole outside our home. I called the power company, they said we don’t do cats. So I put food and water at the base of the pole hoping to lure him down. It was August in CA, 100+ temps, so I was worried about him. He began to make his way down and jumped down on the transformer on the pole. He made contact and was electrocuted. I thought “Oh %^&$, now we have to watch our beloved pet decompose in front of our home”. He then began to convulse, slid off the transformer, hit everything he possible could on the way down, then hit the ground (not on his feet I might add). He took some deep breaths. I ran to him, and felt his little heart racing mile-a-minute (V-tach? At what point of the cardiac cycle did he get shocked?). I brought him in and called the vet.
After losing his tail and part of an ear, he turned out ok after all.