Twitter allows many automated functions so you can build your community, or “tribe”, with less effort and with a wider reach.
When used correctly, these tools indeed grow your follower count. (How much you want to focus on quantity alone is a different matter.) On the other hand, blindly following and following back may result in a situation like the one in the image. Following two thousand people and being followed by more than 400. The guy has even managed to get listed twice. Without one single tweet.