Accessibility is usually viewed from the standpoint of a person who uses a wheelchair being able to get access to the physical environment. Ramps, wide doorways, door handles, rest rooms, etc. All of this stuff falls under the heading of 'Universal Design'. This design makes it easier for a pregnant woman, a family pushing a stroller of kids, the UPS guy with a loaded dolly, you get the idea.
Accessibility is truly more than just getting in the door. We are talking about Equal Access. According to Wikipedia, : "equal access to social, political, and economic life includes not only physical access but access to the same tools, services, organizations and facilities which we all pay for." It's a civil rights issue. Just because a person has a disability, they should not be discriminated against. Similar to rights for women, blacks and Hispanics in our society.
Let's not forget about how big an issue like this is. It's not just about parking...