I don't need a different backstrap size, I'm right-handed, and I unlike a lot of people I don't mind the finger grooves, so I've never seen a need to get rid of my old Gen 3s and go to Gen 4 or 5. In fact, all the Glocks I've bought since Gen 4 was released have been used Gen 3's. They're cheaper and there's no downside for me. It keeps me from having to stock spare parts for different generations too.