One consequence of that could be that you can only have music you purchased in the iTunes Store in the cloud. What about music bought in other stores? What about music ripped from CDs? Indeed, what about pirated music? Amazon’s and Google’s cloud lockers work with all those files, will Apple’s?
If it doesn’t, its usefulness will be quite poor compared to what Amazon and Google have to offer.
Given that the labels were quite miffed that Amazon and Google allow you to upload arbitrary files I would be surprised if they moved away from that position.