People take pictures during construction to show their family, to ask the builder questions and to document the process. One of the biggest reasons to take pictures during construction is to have a record of hidden conditions.
Prior to enclosing your framing, electrical and mechanical with insulation and drywall, thoroughly document where everything is. The same goes for pictures prior to pouring foundations. When you need to locate a stud, a wire or a pipe later it will save you and with digital cameras you really can’t have too many images.