you mean specifically performing differently than they actually are, not forcibly better than they really are
The thinh with cars nowadays is that the ones that have these synthesizer boxes for the most part are turbo cars that are meant to be sporty models. Look at the GTI and the F10 M5 (2012 model+), they have turbos, which muffle the engine note.
Cars like the BRZ/FRS and the Mustang don't use a synth box because the engine is loud enough without a turbo to produce the desired effect without the box.........
Sure there are special cases where some cars are so quiet regardless of aspiration type where the sound is simply played through the speakers. I know specifically 2 cars which do this.......
But at the end of the ay, I don't think it's such a big deal since people who want the cars won't forego them for something as petty as noise generators or sound piping tubes.
They can be defeated if desired and if they really annoy the owner....The tube in the FRS/BRZ or Mustang can be removed. The fuse can be pulled from the GTI or F10 M5.
I've never decided to not buy a car because I can't hear the engine naturally...Have you?