Power and fuel economy are not the only two variables. Emissions are the biggest thing that comes to mind: your new high-performance remap might put your car outside of the emissions limits for your market.
Some aggressive remaps can also adversely affect how the car drives in normal use. Think rough idle, or jerky acceleration. The vast majority of drivers do not want that.
I had an E30 BMW with one of those. Push the button and the automatic transmission would immediately downshift, and the engine would spin up in a hurry. Spaz mode was fun.