I understand what you're saying Adam, believe me, I do!
Until about 2 weeks ago, I had a skip on my front drive.....I'd been installing a new kitchen for my next door neighbours and as their driveway is a lot smaller than mine, I offered to put the skip I needed for the job on my own driveway for the duration of the works.
My wife works from home and the skip was sited just in front of our lounge window and she became aware that someone was in the skip as she could see them whilst she was sitting & working.
She went out and challenged them,....2 guys in high vis jackets + hard hats....asked them what the hell they thought they were doing, only to get what she assumed was a load of abuse in a foreign language.......
As I said earlier, I'm pretty sure that if someone took the time just to ask for permission to remove something from a skip, 99% of people would be fine with it......Its just the thought of strangers taking it upon themselves to go through any of your property, whether it's in a skip or not, is a bloody liberty, as well as being illegal!