I use LinkedIn fire the sole purpose of promoting my research and the FOSS projects I work on, with the hope that if the right people see it, it can help what I do make a positive impact.

In that case, high engagement means more people see my stuff, which means a higher likelihood of the right people seeing it.

However, I'm sharing stuff that I actually hope is useful to someone out there. For people just circlejerking it's just for the ego boost.