Sure, to be mass market you need an ecosystem of apps, which is sort of a feed-back effect.
However a niche market only needs the apps that, well, that niche needs.
If Google themselves can make a killer app or two, everything else might as well be a bonus.
I honestly think theres lots of very specific use-case's for Glass (and other AR HMDS). Certain jobs it might be useful for - anything where hands free access to information is useful.
Admitably, I haven't seen much apps on Glass focused on those more practical use-cases, which is a shame as I suspect it would be a much easier market to grab
first. I mean, if you use Glass for your job your less likely to care about its style.
Remember the first mobile phones or laptops where very big, very expensive and not very stylish. For that mater, so was the first gameboy.
If Google can provide a function for their specs beyond "hands free smart-phone", then it will get a foothold regardless of other factors.
As for stuff being near the eye you can get very good glasses now for $100 up, including lenses. Or very accurate digital watches for only a few dollars.
I think your oversimplifying having a display kept in focus that close to the eye - and presumably made to a good enough standard to withstand years or use without changing much.
I admit, I am just guessing here, but I don't think its as simply as a LED and a good lenses. I know at least Vuzix have some wave-guide technology which I think is some method to channel light to the eye so it focus's correctly. That might be more necessary for "standard lens" look rather then the Glass style above eye display though.