I wish people would engage their brains while waiting for parking spaces. If you see a person, on their own, walking briskly towards their car, keys in hand and no bags to load, it's probably a reasonable expectation that they'll get straight in the car and go, unless they indicate to the contrary.
If you see someone with multiple small children in tow, including a small baby, laden with stacks of shopping, one child screaming that they've done a poo, a buggy, rummaging in their pocket for their keys, there's probably no point holding up a queue of traffic and tapping the wheel, while gurning with impatience. They're going to be a while!
I posted before about a very strange space in the multi-storey in town, where I've twice been harassed for the exact same space, despite there being multiple other empty spaces within about 20 feet. One was an oldish couple who lurked and glared and, if I remember rightly, beeped, holding up traffic for ages, and then waited till I'd gone out before choosing an entirely different space 
Not even an adjacent space!
The other time was a woman with children in the car - so you'd expect her to have some awareness of how long it takes to load children - and again, there were multiple other spaces, some of which were substantially bigger than the one I was in. I had a very tiny DS2 in the sling, and 2 year old DS1 in the buggy, as well as quite a lot of shopping. She waited and glared and edged forward while I loaded the two of them - fortunately not holding anyone else up this time. Then when I went to put the bags in the boot, she leaned out and said 'Could you take any longer?' To which the obvious reply was 'Why, yes, yes I can' So I did 
There's clearly some sort of magic about that space.