It isn't just about businesses. There used to be a lot more free apps on the Play Store, but keeping up with constantly-changing requirements makes that impractical. You can't just put something up and leave it. You have to work on frequently or it gets dropped. You also have to keep up with their demands to limit certain features and to provide new information or it gets dropped.

I used to have a handful of free apps up on Play. Now they are all gone because I just don't have the time to rewrite them every few months.