You didn't (and don't) see PC developers develop games for the lowest common denominator. You see them develop games for the smallest minority that has high end machines.
I think over the last 5 years, as developing for both PC and console platforms has become more common to help offset some of the huge development costs, you DO see PC developers develop games for the lowest common denominator. In this case, it is considered to be game consoles.
If you look around at PC gaming forums you will probably find people lamenting that "PC gaming is dead" and "consoles ruined PC gaming" because many developers seem to concentrate on their console versions and do a half-ass port to the PC platform that performs poorly or has bugs and intrusive DRM. You'll see games that aren't really tailored to PC-specific control schemes--mouse support just slapped on but the UI is still geared towards a TV and gamepad control. The graphics will be the same just that sometimes you can run at higher resolutions and maybe enable antialiasing and anisotropic filtering. The textures won't be any higher detail to account for more video memory available with PCs. The geometry of the levels or models won't be any higher, either, for the more powerful PC video hardware.
And really, if you want to maximize your investment nowadays, you'd be stupid not to make sure your game can run on as weak of PC hardware as you possibly can. Games like Crysis are the exception, not the rule. The $3 000 000 000 USD game franchise Call of Duty doesn't require much hardware to run and has probably had most of its sales from its console versions (I'm too lazy to try and find NPD breakdowns to confirm). If your games now cost a few million to create you gotta make that money up somewhere.
