Any developer (or writer, musician, athlete, parent, human being...) worth their salt is constantly trying to improve their skills. The best way to do that is not only through doing something constantly (read: practice) but also through research, reading, and studying new material. That's why school is a thing that we do.
One of the great things about Android's ecosystem is the number of indie developers who are able to enter the market successfully, providing a great product and inspiring would-be developers to join in. For many though, Android development in general is a mysterious topic. How an app or game goes from an idea to an entry in the Play Store is unknown, but (thankfully) not unknowable.
Of course, considering how major development studios bring apps to life doesn't require too much thought – major companies like EA, Disney, or Rockstar have no problem hiring designers and developers to crank out and maintain polished apps.