a lot could be from not paying attention and many times this isn't really the case.. I owned and operated long haul for 18 years, One time in Detroit I backed down a long alleyway, took down an electric line between the buildings,, I honestly didn't see it when I looked first. Anyway, after unloading a DEC 10 system, which takes about 6 hours,,, The electric company came back and replaced the wire in the exact same spot, I took it down again on the way out,, The owners of the building threatened to sue and all sorts of jirations,, When the electric company came back I asked why they didn't follow laws that dictate the wires at sag point be at least 13.8 inches off the ground,, The building owners then finally backed down,, THey had never had a delivery prior to me much bigger than a one ton truck.. I assume the wiring was brought to code,.. SO a lot of reasons can happen in taking down wires,, Something I wouldn't fire a guy over unless problems start happening one after the other,