[ultrasaurus]

I suspect the follow button exists primarily to train the advertising algorithm -- how much more would you pay to show a political ad to someone who "followed" Nikki Haley or show your Honda Civic aftermarket parts to someone who "follows" Honda vs just a demographic match.

[fzzzy]

The follow button exists because feeds used to be reverse chronological, and that fosters community.

[Gigachad]

I suspect the average person just does not carefully curate and prune their follow list. Youtube lets you see stuff only from channels you subscribed to. The content tends to be a lot less interesting than the usual front page.