All true but I think the more central issue is, whether or not the person who will live in the house (or drive over the bridge) is present during construction,

All true but I think the more central issue is, whether or not the person who will live in the house (or drive over the bridge) is present during construction, and knowledgeable enough to notice whether things are being done well. In general, the answer to one or the other is "no". The only exceptions are, as you say, in multimillion dollar custom homes, and then only sometimes.