Increasing the resolution does little good if the lens can't resolve enough detail to take advantage of the extra pixels.
The extra pixels wouldn't help with anything, in fact, and could even hurt under some circumstances.
The extra pixels yield an exceptionally sharp image, which partly makes up for the smaller screen.
Also, are all those extra pixels actually good for anything?
That'd sure solve the problem of where to get all those extra pixels, but I'm not a fan of this approach.
And for the money, many people may decide that the extra pixels are unnecessary.
Without these extra pixels the resolution would cut in half (for each eye) on the horizontal or vertical axis.
The camera may also use the extra pixels for digital image stabilization.
These extra pixels are a weighted average of the adjacent pixels.
Some other choices exist, notably 23" and 24" units with 1920x1080 resolution, but we prefer the extra pixels.