I'm not quite sure why you've taken the attitude you have. The condensation issue takes place on all cars, not just your car. My old car had permanent condensation in each light until I removed the covers, heated the light up to evaporate the condensation, then blasted cold air through to ensure the damp air was out, and then fitted my new covers.
Try to avoid massive puddles will stop unnecessary spray potentially going into your headlight, thus reducing the chance of moisture getting inside. Could also try a couple of little silicone gel packs to collect some moisture too.
I'd say its more like the builder saying 'Ok that's it all you have to do is clean the windows'.