You cannot tell by looking at someone whether they have a disability or not. Not all disabilities involve a mobility aid or visible condition. In my own family we have someone with MS, who only uses mobility aids part of the time, so you could see her get out of a car and walk off without any visible disability (and indeed she requests a wheelchair at airports, and will get out of it at the end and walk to get into the car - using a wheelchair doesn't mean someone can't walk, and getting out and walking doesn't mean someone doesn't need a wheelchair!), as well as someone with Ehlers-Danlos syndrome, which also has no visible cues but which causes hypermobility of the joints and frequent dislocations - and me, who has a chronic illness that causes extreme exhaustion, with no visible external symptoms. It is ridiculous in the extreme to think you can tell someone doesn't need a disabled parking permit from looking at them for a couple of minutes in a parking lot - and nor is their medical condition any of your damn business.