[cygx]

Any decent C++ compiler should be able to inline generic code while C often relies on function pointers.

What makes you think that a decent C compiler can't inline runtime-generic code using void* and virtual functions?

Sure, erasing types only so that the optimizer has to figure the information out again using constant propagation is far from optimal, but the underlying issue is actually source code inclusing vs modular compilation -- most of the speed gain of templates comes from the fact that it only works with the former, whereas C-code traditionally does the latter.