Because, other programming languages usually don't have as good as results. C/C++ is a much more flexible program to use IMO. Assembly mught be good, too. Take Zsnes for example, most of its code is in ASM, with this you can run something very fast on a very slow computer (i.e. 60fps on a 400MHz CPU). But the problem w/ASM is that some things can't get emulated properly on Zsnes, like the SPC700.