There are good reasons to have a professional inspection performed on the brand new home you are buying.
Buying a new house is likely one of, if not the largest purchase decision you'll ever make. The whole process is fraught with emotion and stress. A professional home inspection will substantially reduce the risk for your large investment in a new home. It just makes sense to learn as much as you can about the quality of your new home, before signing off on everything.
Building a new home is a tremendously complex endeavor. It involves many people, usually split up into sub-contractor groups, each working on different parts and systems of the house. Even for the best builders, its nearly impossible to complete this process without missing something. Maybe its a plumbing fixture that didn't get tested for leaks, maybe its an electrical box that isn't working, or any one of dozens of minor problems that can easily be overlooked in such a major undertaking. We will find such problems while it is still early enough for you to bring them up with the builder and have them corrected before you sign-off and start moving in.
For the relatively small cost, a professional inspection of your new dream home can pay big dividends in peace of mind and getting any problems identified and corrected before they can become an unpleasant surprise.