I use SM very seldom. But IG was my fav for a long time. I only had about 50 friends, all real people that I knew, they didn't post daily, it was roughly 1:1 ratio of follower:following, so - I could open it up about once a month, scroll through a dozen or so images and see the "you're all caught up" notice and bounce. At some point, I remember it saying my account wasn't showing me Ads because I had low follower count / low engagement - which I thought was great and it went on that way for a few years. Then at some point it became clear it changed. At first, it wasn't Ads, just posts from random people inserted into my feed. I never engage with anything overtly - no likes, comments, etc. But, I think I do spend more time on things that I "like" and do swipe through if there are multiple images if I find something interesting. So that was all the training that it needed. Soon after that, all I see on IG are half naked women in form fitting attire and construction content. Turns out I'm a hetero male that has a hobby of building stuff/home improvement, but I already knew that. I stopped using it all together.

The funny part is because of my construction hobby & interest in building science; I started seeing Ads in Spanish which I don't speak. I get this on YT too as that's where most my "how to build a ...." stuff ends up.