You would think if your job title is "cable installer" that you might actually be trained in installing cable.
I don't know about the rest of the country but in my area (Northern California) most of the installers are "independent contractors" and get paid flat rate. So they get $75.00 or whatever per install, I'm sure this doesn't help matters any. I know a person who is an actual employee of Comcast and his job is to follow behind all these guys and clean up their mess.
I too have straightened out many a comcast install. After having my first HD box installed by Comcast and arguing with the installer about connections, etc. (I finally gave up, let him do it his way, and then took it all apart when he left and hooked it up correctly) I now just go straight to their office and pickup the box and install myself