@Markerrag -- What's wrong with putting up entire compact discs? Those just give people more choices. Also, CDs increase the capacity of the machines because they don't take up as much space as old records. That means more music can be offered. Usually that means a bunch of different genres are represented and you have classic rock on hand, too.
As for owners not changing these often enough, that is the fault of the people that own the machines and not the jukeboxes themselves. Besides, perhaps these aren't changed as much because they are not as popular as they used to be. Jukeboxes used to be all over the place, but they are comparatively rare these days. Why spend a lot of time and money maintaining something that probably isn't bringing in a lot of customers?