Ask HN: Why are social media spam bots still a thing?

Specifically Instagram. After many years, I still get regular messages from spam bots, usually pretending to be women that are romantically interested. It seems trivial to ban (or even prevent) those accounts, from a technical perspective. Reporting them also doesn't seem to do much. Why is this still a thing? This should have been a solved problem years ago no? Are there, besides technical reasons, other reasons to keep spam bots alive on their platforms?