I would think it would be more like the problem that colleges face in choosing who to accept. Companies offering apprenticeships obviously have limited resources for managing and running the program, but on the other hand perhaps apprentices can be "expelled" more easily than full-time employees.

Perhaps this is what that one financial firm was on to when everyone ridiculed them for their "Pay us to work for us" scheme (which does sound ridiculous, unless perhaps you can sell demonstrable educational and networking value from the program and can frame it as competing with what colleges offer).