They certainly know more about home construction than about home systems. That is why you will need to be persistent in most cases to get what you want.
Many builders focus only on TV and telephone outlets and their placement.
You may need to make sure you are getting the all that you need and want. This facilitates easier changes in the future and provides the purest signal quality. For telephone, ask for data grade, category 5 wiring. This will server your internet requirements better. For TV, the RG-6 or Quad 6 cabling is superior and carries a higher bandwidth rating as well.