If kbin's microblog automatically boosted everything I upvote, whoever followed me or anyone else would have a timeline brimming with random comments from other users who said absolutely anything that anyone else liked reading, and it would be the least interesting thing nobody wants to deal with.

We're talking my whole blog being just one-sided repeat documentation of every conversation I've had, because even when we don't agree, I like showing appreciation for an enjoyable interaction. We're talking every fair point or inquiry on mine or anyone else's post. Weed killer reviews. Someone's socks that I liked enough to pat them on the back for, but not enough to bother people in my life about.

Following anyone would be unnavigable noise and would result in both complaints and an overall chilling effect as to whose contribution is good enough to warrant any attention at all. The platform really benefits from being able to make the distinction between "nice, interesting, thank you" and "nice enough that I'd brag to my dentist," imo