So, whenever you are standing behind a woman who is not packing her shopping, and has not got her money ready, but is aimlessly gazing about her, you now know the reason.
My OH was amazed when I told her that the pay-on-exit car-park in a nearby shopping town was free up to an hour. Apparently, such an eventuality had never come up before...
Personally, I was far more surprised to find out shopping can take more than an hour.