There is nothing fundamentally wrong with either:
- An emulator sacrificing accuracy for performance
- An emulator sacrificing performance for accuracy
That said, MAME is a huge
project, and there needs to be some organizing principles. If MAME started trying to favor performance over accuracy (even on an optional basis), where would one stop? Favoring accuracy also has major advantages from the perspective of ensuring that the emulation of common hardware components are properly vetted and kept accurate.
If you don't like this, by all means fork MAME and re-add the sample emulation. MAME will continue to function as a documentation project and your fork will appease the people that want to run the games on cheaper hardware.