I have to say, I have never encountered a program where compiling without optimizations made no difference. If you have seen that, then I would agree that C was a very, very poor choice for that particular domain.
It made no measurable difference. The acceptance criteria for the system were not materially affected. Since the optimization did not improve the performance by that, it was generally set one way ( mostly off ) and let that way.
Teams I'm on have written some tight - but readable -code, too. Well-architected, low-latency, low-jitter.