Judging by the number of Lost Pet signs that litter the entrance road to the big housing developments in my area, I'd say this is the most likely explanation for most of the stories.
It tugs the heart strings (awwww, kitty came home) and hints at the supernatural/unknown, so the one in a million that make it get reported.
"Cat failed to learn road crossing skills in time" and "Cat got adopted by family in housing development five miles west" don't make good movies.
I would also guess that the majority of "lost cats" are squashed, and either merged with the roadside or shoveled up before the kiddies can see them. Of course, some just do get lost in some way. In addition to my "cat came back" story above, my mom had a cat that disappeared and turned up weeks later, nearly starved to death, inside a nearby house that had been under construction. He had wandered in just before the builders closed up the house while awaiting materials or something. Cats are very tough and tenacious little beasts.
Cats also vary enormously in their survival skills. I live out in the country, with no cat of my own, but a big pest-filled old barn, which all the neighborhood cats frequent. I can't recall how many squished cat bodies have appeared in front of my place over the last 20 years, but it's pretty clear from that and the changing population that some of them just don't have what it takes. On the other hand, one grizzled old puss came around for years without risk, despite living a quarter mile down the road. Nearly every day we would see him hunting around, often heading home with mouse in mouth, safely crossing the road through the culvert, until he became too old to make the trip, and eventually died of old age.
I have yet
another lost cat story, from my ex wife. She grew up in Switzerland, where I guess people think differently about such things. They had a cat, which "disappeared." Some time later, she was rummaging in her parents' closet, as kids often do, and found the cat's pelt, nicely preserved. There does seem to be more than one way to skin a cat.