Last week I had a courtesy car with parking sensors and it went frantic as I was reversing beside a plastic wheelie bin. No amount of "Yes, dear. I can see it. It wont hurt you. It's only plastic" made any difference.
Seriously, they are a big help, and probably help avoid many scratches & dents. Now we need automatic reversing control for drivers who just can't master it - most of whom I seem to meet on North Wales' country lanes.
Frank (G.O.M.)