Firstly, to "optimise" is fine. Making it lousy for anything less is not optimising and (as shown by other sites) it's not necessary.
Secondly, you're totally missing the point with those stats. I run a screen resolution higher than 1024x768 too. But I have a number of other windows open for other applications and never run my browser in full-screen mode. It's called multi-tasking. I've seen polls suggesting that about 50% of users run their browsers full-screen. For the other 50%, the screen resolution is totally irrelevant except as an upper limit.
Do you have stats on what size people's browser window is? Even then, that would be misleading, as users will be making their browser window bigger on this site precisely because it works so poorly otherwise.