Some people are plain stupid.
I had to guide a mahoosive (for our river) boat under a bridge today when I was out for a walk. (Down south) Some people off on holiday hadn't thought things through. They had inches to spare between them and under the bridge span (they scraped their canopy) and therefore they had to duck below their cabin and steer blindly while I shouted vague instructions and encouragement.
It was very trusting of them really. Especially as I forgot to warn them as the next bridge along was substantially lower. 