I was old enough to know better, but I knew a couple of younger people who were doing it because "it was easy" and policing of such things hadn't caught up to the internet yet, so for someone at their age they would have just considered it to be "dumb stuff on the internet".
It doesn't translate to today's Internet.
(This would have been ~25 years ago, maybe a bit more)
Probably depends on how they acquired them (breaking into an online store's payment transaction database / trading for the CCs on IRC / lifting them using a physical skimmer / etc.)
Yeah, I never actually used or shared/sold any of it since it was mostly a game for me. But nowadays I understand it is a very bad idea even just to store this kind of stuff.
That goes well beyond doing “dumb stuff on the Internet”