Yeah, why do people follow us? I ask that same question. You would think that if you suck, then you'll lose followers, and that does happen to some degree. But more so, most people run around on Twitter, Facebook, and YouTube, following people, and it is a habit many fell into for the past ten or more years, since the early 2000's for many people around the world as a trend, and addiction, and I fell into that habit at times. People take their habits onto Steemit, generally. Yeah, there are exceptions, but people tend to do what they do on Steemit whatever they have been doing on the other social networks for so many years now, both good and bad habits.
You are probably right. Personally I only follow people I am interested in and do my best to keep that list up to date across all social networks. I unfollow not just because people aren't very good in my opinion but also because my interests have sometimes simply changed.
It i like pruning a rose bush.