I hear you, coding on a widescreen monitor is annoying. All that space, but half of it is useless. The only nice thing is that you can have your tool bars on the side without sacrificing too much horizontal space.
I bet some of the reason that they can't just allow games to work at any resolution has to do with testing. The companies probably test at the given resolutions and don't want angry users complaining when something doesn't work properly, especially concerning different aspect ratios.
As for complaints about 16:9 vs 16:10, the difference is barely noticeable. It is kind of annoying if you've just bought a new 30" display, but the 16:10 resolution won't be phased out of games for many years I'm sure.
I'm sure when Duke Forever comes out we won't even notice, you know cause we'll be busy eating our hats, wondering why hell froze over, and running away from the flying pigs.