I upvote manually and have some of my friends automatically follow my votes.
I never go searching for content out of my own Feed though.
So I only vote people I follow.
Probably because I have gotten used to checking my feed daily and picking out best posts from there and also because searching content outside my feed is too time consuming.
I think this is common, since most people don't have time to read all the posts that are written. Communities at least potentially allow people to select areas in which they are interested, rather than just following known authors.