I agree with you in the short term, but I think Valve is playing a long game here. The current Steamboxes are inferior to consoles, but in a few years when you can get a Steambox with better specs and the consoles haven't changed it may be a different story. And when the next generation of consoles doesn't have backwards compatibility, but Steamboxes do, the game selection problem will be gone. If they're targeting for the long term, they don't need all the secondary services right away; they need the base platform to be stable and then they can start pushing for compatibility (Skype already runs on Debian, but Netflix will be important).
Right now they're just trying to bootstrap themselves out of a chicken-and-egg problem. We probably won't have a good idea of how successful they'll be for 5 years.