I think a lot of the time it's that people just don't think, but that doesn't help when you have the inconvenience of dealing with the results...
Incidentally, the District Council have got back to me already and say they've forwarded my email to the County Council, as apparently they're in charge of that sort of thing.
I think delivery drivers are trained to find the most inconvenient place to stop, even when there is a really logical and non-obstructive place for them. Rather like bus drivers who refuse to pull in even where there is plenty of room.
Incidentally, the District Council have got back to me already and say they've forwarded my email to the County Council, as apparently they're in charge of that sort of thing.