Each "follow" creates both an increase in one of both followers and people being followed.
Since not everyone is of equal interest I imagine what you have observed is true of every form of social media. For example, if Kim Kardashian (for example) has 1 million followers, of those million Kim Kardashian may only be following 10. Thus 999,990 people would be following more times than they are followed, 10 would be followed and following an equal number of times and 1 would be being followed more than they are following.
It's not a random allocation.

I'm the opposite last time I checked. I follow three people and have over twenty followers. That is one part of this site that I don't keep up with much.

Don't know is my answer, I have one more follower than I'm following