I haven't noticed if it was like this in GTA V as well but in older GTA games, up to GTA IV, once you rode a car that is quite unique, or a sports car, the NPCs will also have it making it uncommon. It's kind of funny and annoying though. Because almost everyone have it al of a sudden. But hey, at least it won't be tough to look for one once you need it again, haha.
