You'd think streamers would be more careful

I mean, if you stream LoL, or any other game which gets you a lot of views and donations to the point where it practically turns into your job(or at least benefits you a lot), then wouldn't you really want to make sure you don't get banned from whatever you're streaming because you're making profit off it? You wouldn't upset your boss at work to the point where they'd fire you, would you? Sure you could pick up a new game to play, but thats like picking up a new job. Theres a good chance that if the last one ended badly and this is your backup, then the backup won't be nearly as good as the original.

Besides its not nearly as big of a loss for Riot as it is for them. Someone else will simply fill in their spot in the rankings, and a new streamer/video maker will take their spot in those places as well. Even the fans will move on eventually.