Comment by jercos

I think you highlight the exact issue rather well... fixed-point DSP instructions are awkward to use. The FPU and the double-precision hardware with its baked operations work with IEEE floats out of the box, so the programmer can be "lazy." A thousand new programmers can write something like `* 0.7` in C++ inside a tight loop without it stealing 200 instructions from the timing of the rest of the program.