How so? If your car is tuned for 94 then you really have no choice other than to retune it for 91.... unless you want it to blow up because you listen to people like, well, you.
If it's a case of someone thinking their car needs 94 (and there are so few cars sold in North America that do) when it doesn't then yea, but "throwing your money away" is hardly what they are doing.
Once you get into high end cars and heavily modified track/road cars with SAEMs you have certain requirments.
If you're using a highly tuned car as a daily driver, then that's unwise