Hubbell-raco receptacle and switch boxes
How many boxes would you have to manufacture in order to cover everything we use a 4 sq box for. It's just not financially feasible from a manufacturing standpoint. Plus, it would be hard to mount and work inside the box from interference of the plaster ring. So when you say "most of the boxes" you are using them in situations you are working in and does not consider the uses in other types of construction. In fact I would debate that more boxes are used commercially and most of the boxes there are blank covers and you would finish out devices on 5/8" drywall.