What proof is there that the market "wants" it? It's not like the manufacturers gave consumers the option of having it or not having it. I'm sure if there was an option box on the order sheet to have or not have fake sound piped in, NOBODY would check that box.
They do studies and read reviews. People say they want more engine tone but manufacturers cant just produce cars with the equivalent of aftermarket exhausts in terms of dB to achieve this, so this is their only alternative.
If you didnt do it as a standard, then yeah, nobody would check the box because it would be a $750 option and thats stupid. Doing it on EVERY car is probably $5 once you amortize R&D, Material and labor costs and run the numbers out.
Like I said, most consumers that want better tone dont care how its achieved.