Its entirely likely that no accessible parking spaces were required when the project was built, under present codes two spaces would be required with one of them being van accessible. The number of guest spaces is not mandated under the building code but is often dictated in local ordinances and is often a fraction of spaces per unit in the complex.
I am president of my association, 247 units and I can tell you if we could afford to enforce guest parking standards we would. As it stands now there are no guest spaces available whatsoever in our complex because of residents having multiple vehicles, roommates with vehicles etc... I can empathise with you but I can also relate to the position of the board.
As many previous commentors have said, go to a board meeting, find out what the rational is behind the decision, run for the board yourself, get your fellow owners involved and pressure the board if need be.