Oddly enough, the ADA laws were written in a way to use the free market. The government can't force you to be ADA compliant. Instead, it relies on lawyers and their disabled clients to sue you into compliance. An entire cottage industry of law firms who specialize in ADA compliance have sprung up since the law's inception.

Having a few ADA parking spots is fine and a drop in the bucket compared to the wasted space from all that mandated parking.

Also, people with disabilities tend to drive less than those without them.

ADA requirements are outside of the planning sphere though.

In fact, that ADA requirements came from laws from the federal government rather than from urban planning is pretty good evidence that the market (ie democratic legislation) is better at this than centralized planners of urban areas.