I don't want to tar all builders with the same brush, but in my experience many of them (at least in the U.K.) have no respect for power whatsoever. They throw their tools into the back of the van, tug cords out from under piles of debris so that they get damaged, and then continue to use power tools with cords so beat up that a short or contact with bare conductor is inevitable.
Second that. A few years ago our house nearly burnt down from a few stupid carpenters who did some work in the attic. They had an extension cord that was twisted and taped in several places, then they left it plugged in overnight, laying on the wood floor beneath a sheet of cardboard... thanks heaven the lady one floor below called my uncle who came with a helper and a few buckets of water just in time to put the yet small fire out. The fire department came some time later with 7 trucks and compalined heavily that they couldn't find a fire...
On the very same site I saw 2 Polish drywall guys who used the worst stuff I've ever seen on-site. They had the cheapest of household grade Schuko extension cords, the weak plug body broken and repaired with paper masking tape and some similar stuff...
