I don't know, it seems like it's just fun thing to play around with. I don't think serious things are meant to be built on this.
I often want to play simple games like Pacman, space invader, breakout, tetris or some other random iteration. Sometimes there are non-spammy simple versions of this game but often there aren't. This seems like a pretty cool fix. And if they disappear in the future, who cares?
That's precisely how something ends up becoming ubiquitous. You, and everyone else, start having fun on it and then suddenly it's a locked-in platform monetized by them.
YouTube started exactly how you described it, some silly thing not meant to be serious and today powers multiple 100M+ businesses using it for content to reach mass audiences.
> I don't think serious things are meant to be built on this.
I read at some point that projects at Google didn't get a greenlight unless there was a reasonable expectation they could be used directly or indirectly by a billion people.