My hypothetical Java coder would not be "ignoring performance" (it's not like he's using bubble sort) he would simply not care as much about squeezing every possible ounce of performance out of the target system. The minimum system requirements would be low enough, and he will benefit from fast development time and will meet his deadlines without worrying about his code becoming more and more arcane as more performance hacks are thrown in (yes, just because you code in C++ doesn't mean the CPU automatically clocks twice as fast, you just have more optimization freedom)
Sure, you can always ignore the performance of your application and expect the user to buy new hardware. But with C/C++ the minimum system requirement is probably lower and you might sell more.
Besides, we are talking about games here, not some high performance computing application. Most people who care about high framerates already have monster rigs, those who don't implicitly accept that some games may run slower by nature. Following your train of thought, every game should be developed under its own real time operating system, in raw assembly, and coded on-demand for every customer hardware configuration. By an assembly guru. Well, I just don't think that's cost effective, that's all.
And yes, I certainly do expect the user to buy new hardware, so that I can implement bigger and better features in my game instead of worrying about how fast it will run on October 4 2012 at 1:44 AM on current technology. Computers only get faster. Think in more than one dimension.