The ad supported is just the reason to make it addictive. Get rid of all likes/thumbs/follower(counts)/notifications and it loses the endorphins and stops being the problem it is today.

You might not have opened any social media app lately. You need 10 seconds before you're sucked into the feed. Likes are a thing of the past, they just gather your interests by your reaction time on any content they show you.

Hey you spent 500ms looking at this pretty girl dancing, how about some ass now?

I get straight up PORN ads on Facebook too. Twitter at some point showed me porn as well, even if I had specifically curated it to show JavaScript content.

You're not wrong. Even simple "page hit counters" became a target of manipulation once they were common. Human nature is tough at scale.