Totally unacceptable, as over time this kind of behaviour becomes the norm and the reasoning gets weaker and weaker e.g. 8 spaces free out of 10 becomes 5 spaces free, becomes 3 spaces free, eventually "I'll only be a minute"...
I know an ex-traffic warden and the stories I've been told about the excuses people come up with for being parked in a disabled bay would shock you. The most common is "well there are 2 other currently empty bays" - so what if 3 disabled people turn up?
Another common one is "but I'm picking something up for a disabled person". So blooming what - YOU don't have a disability, the bay is there for people who need to be close.
"I was only going to be 5 minutes." They would get this also on double yellows, loading bays (and no, popping in to fetch a takeaway doesn't class as loading!), but stops etc. Doesn't matter, law says "no".
But you "have" to give me 10 minutes. Nope, automatic instant fine. And don't argue that you know better, traffic wardens a) know the letter of parking law better than you as that's their job, b) they have to take exams on this stuff and regular refreshers and c) no most don't get any more money for booking more cars.
They had the retired couple saying they used the disabled bay as there was no other parking left next to the market, and when asked what if a disabled person also wanted to visit the market said "oh dear, I hadn't thought about that"!
I have a blue badge, I can be in a LOT of pain if I have to walk more than about 30 metres. But I moved out of the disabled bay at work a few weeks ago because it was 9am, loads of people were starting work, and at least 2 of the other disabled spaces (out of 5) had non-badged cars in them. Then my friend who is a wheelchair user turned up to start work. I gave up my space for her as her need was greater than mine, but what about the cars parked there who had no need? I ended up in a LOT of pain that morning having had to walk well beyond my comfort level, to the degree that my boss took one look as I got to my desk and told me to sit down & she would collect the post (usually I do that) and make my tea on her way back, and that I wasn't to move for at least an hour except for the loo.
The entitlement and/or resentment some people have over using disabled parking spaces can be breath-taking. There is one person who brings someone who visits our building 2 afternoons a week (not staff) who insists on parking his car in one of the disabled bays then sitting in it as long as their passenger is in the building - even if the only free one is further from the doors than a non-disabled bay. No badge of course, and was aggressive and sweary to me when I reminded him about the bays. Also told me he was "just waiting for someone" - for 3 hours. Unfortunately we have no way of stopping people using our work car park, and the reason for visiting is valid, so there isn't really much we can do.