[nottorp]

For the people who can't hear the vacuum cleaner noise from their PC because they use headphones yes, getting 7200 rpm at the price of 5400 might be nice.

For the people who want to run cool, quiet and less power hungry devices, they'd like to get exactly what they ordered. Nobody buys a 5400 rpm hard drive for speed.

Stick a 7200 rpm drive in a console and see how the cooling system copes, for example. Or a low power PC with a PicoPSU. Or a NAS.

Some portable hard drives can be powered off USB. If you get a 7200 advertised at 5400 drive, it won't run because it's not getting enough power.