I've worked for manufacturers. It used to be a standard procedure in the ongoing cost reduction exercises. A bright young lad fresh from college would come along and ask why each car had an individually specified wiring harness, as it would be more cost-effective to make them all the same for all cars, and would reduce line stoppages for cars waiting for their individual harness. So we went to standard wiring harnesses. In the next round of cost reductions, the next bright young lad asks why we are fitting all this unnecessary wiring to cars which don't have all the items fitted that the harness has wires for, and wouldn't it be cheaper to have individual harnesses for each specification? After all, it should all work with just in time manufacturing.