It’s the one thing that all (or most of us, I guess) have in common; we’re all here because of what’s going on there. It’s natural to want to talk about it.
It’ll pass; I’m already seeing a lot of non-reddit content on my home feed now, whereas day 1 it was probably 95% posts of the sort you’re talking about.
Experience, mainly.
I used to run a phpbb forum, on average the bot signups outnumbered the real people 10 or 20 times. And that was with some fairly robust anti spam measures in place - something I think this platform is too new to have properly sorted out yet.
I may be wrong, I don’t know how the back end here works, but any place where people can post publicly will be infested with bot signups very quickly. The only real variable is how good the anti spam measures are.