Recruiters use GitHub profiles as a proxy for engagement and, I would assume, amount-of-stars-in-pet-project to be used as a KPI in this measurement.

I think that's asinine but I don't make the rules.

That's not how I evaluate people when I'm doing the hire.

GitHub Trending Repository lists, for one. Some (idiot) third party sites use stars as some weird approximation metric for "quality" or "usefulness", for the other.