Your browser example doesn't really work since most websites are smaller than your native resolution and also there are scrollbars for when things go off the page.
I can't think of any games that had this feature, and I am a game developer, so unless I am missing some obvious counter-examples, I think those points are the reason why.
What do I know, im a consumer ... I was just referring to one program that did it because it helps some people read...-
If its too hard, well I wouldnt know really, seen a few games with scaling UI though.