A good chunk of it is that text is unreadable in current headsets unless it's far larger than what most people are used to. So that 720p hololens gives you at

A good chunk of it is that text is unreadable in current headsets unless it's far larger than what most people are used to. So that 720p hololens gives you at best a 720p monitor's worth of text at a time[1]. Sure, you can have any number of virtual displays around you at any desirable resolution - they're just unusable until you get close enough that you only see a tiny piece at a time. To your specific example of "You could have one virtual display with close to your face for high resolution information, and then dozens of peripheral displays further back for ambient information.", yes, absolutely. That makes sense. But the "close to your face" one would show you less than a paragraph of text, if you could actually see the peripheral ones all the time. Useful at times, to be sure, but not equivalent in all (I'd argue "most") situations. [1]: plus some fudge-factor, because you can read a bit better than with a comparative screen - the change in how the text lands on pixels as you move gives you a slightly higher "effective" resolution... though text at this size is still plenty difficult to read, so you still don't want to rely on it.