I don't think that's the reason for requiring games to be installed to the HDD. It's all part of a grand overarching vision that makes things as painless and streamlined as possible. They also require it (and Kinect) so that when a developer makes a game, that will be a standard unlike this gen where they had to take into account arcade models without HDD's. Doing it this way is less trouble for developers and makes things more standardized and consistent.
That is also a step in the digital only direction that they are trying to go to.







