Just noting that often they're used to drop someone off, then whoever did the driving parks where it's more convenient for the disabled person at a later time. My father has one where he has to limit his walking. But my grandmother had a walker, and she had a lot of difficulty just waiting too long to be picked up.
So there's always the possibility that whoever is driving the car doesn't need it, but it's being used for someone else who clearly needs it. The key is whether or not the purpose of parking is related directly to the transportation of the disabled person. The law in my state says "reasonable proximity", which leaves a lot of wiggle room. I would think that if I'm taking my dad somewhere and I can't find parking (to be close to him) less than a block away, reasonable proximity includes the closest parking that I can find. But someone else just sees me hopping out the car and thinking I'm misusing it. Here's a take from a law firm:
You Were Using a Disability Placard Lawfully
Individuals in California are legally allowed to transport people with disabilities. If you are providing a ride to a disabled individual, you may park in a handicapped space using their disability placard. This applies even if you drop a disabled individual off at the door to a building and then park your car.
