> They also don't work on old.reddit much at all these days, so any effort they have to put in to handling bot traffic is kept to one route.

I neglected to editorialize this part, but I suspect this is because *they don't have to*. I don't doubt that there are some new things on Reddit that people like, but Reddit was functionally complete as a place to interact with other people when it was launched.

I'm not an internet historian, but sites akin to Reddit have existed for a long time, and my understanding is that it happened to take over when the last forum aggregator died for whatever reason.