I am considering building a new home with a builder that does not offer the DuPont home wrap (or similar product) over the exterior walls under the vinyl siding. Would it be a bad idea in the long-term to own a home without this useful feature?

First of why doesn’t he offer the house wrap? If you are the one paying the bill any good contractor should give you what you want, not what they want. I would recommend you tell him you want the house wrap (and any other features you want incorporated into YOUR house) or you will use another contractor. I believe he may reconsider offering the house wrap.

The use of house wrap under siding is a very useful thing provided it is installed correctly. All joints and openings around doors, windows, etc., should be taped to provide a good tight seal. It will keep the wind from blowing through the walls. Siding is not a perfect seal from air infiltration. The house wrap takes care of any air leaking in around the siding to keep it from entering the house.

I run into this type of thing all the time and it really ticks me off. I am willing to listen to any advice someone may have to offer, but in the end, as long as I am paying the bill, I will decide how to spend the money and there is no room for discussion. Give me what I want for my money or I will find someone who will.

I may have come off a little strong here, but I have strong feelings about this type of thing. Especially when it comes to something that is as large an investment as a house.

Is the biggest concern about not using Tyvek more of an air infiltration issue or should I be more concerned about water getting in and damaging the OSB board under the siding?

The main purpose of a building wrap is air infiltration. It will help some to protect the OSB board but that is a secondary benefit.