On what devices is that really a good tradeoff? On mobile, sure (at least, on mobile devices like Apple's that don't have SD cards), but on a regular computer? I find it very hard to imagine that most people are more constrained by storage than bandwidth. Internet access just isn't that good. I can barely stream music over WiFi in many public places (coffee shops, airports, etc.).

If that's really the rationale, I think they're either optimizing for a use case that I find personally very atypical, or they didn't do their research.