It's actually key to obtaining a supermassive audience. People will roll their eyes at me for this, but one of the major reasons that FarmVille was able to reach 80M monthly actives was due to aggressive performance optimization at the bottom end and progressively turning off graphics features based on frame rate.

Nope, as a gamedev I can say that it definitely is impressive.

As with all optimization it is hard: as you try to squeeze more out of the machine your code gets less and less elegant.

I agree as well. Most of my fastest, "best" code is awful to look at because it has to be. It's full of crazy comments and hacks that were necessary for the hardware, language, and time usually. I think as processing power has increased, the low-level code is actually much less ugly. This is in no small part due to astronomical leaps in game design, engine design, and development time and other resources.

Still, in my experience any codebase that pushes a large amount of technical boundaries tends to be full of huge "WTF is this" moments that require explanation. It is an achievement if you can create a decently powerful codebase that can survive rapid changes and additions. It's much more common, but I've seen and worked on AAA codebases that would break if you blew on them.