Below I linked to a blog post by my Sales Manager, Erin Cestero, at JBGoodwin that succinctly and clearly lays out the reasons for using a Realtor® in your purchase of a new home from a builder. Having a buyer's agent to represent you makes sense because the new home sales person wants your Realtor® to bring other buyers to the office. New home sales people know that treating a Realtor's® client right will encourage them to bring in other clients which adds money to the bottom line for builder they represent, as well as their own bottom line. And remember the new home builder pays your agent's commission even though your agent is employed by you to put your interests first. Some people mistakenly think that they can save money talking to the new home sales person themselves. However, it's just not true. The builders expect to pay buyer agents and have budgeted for it just like they budgeted for all their marketing. The incentives and benefits builders give buyers aren't coming from what they save if you don't have an agent. What you're really doing is allowing the new home sales person to keep both sides of the commission for themselves. 

Check out Erin's piece. Oh, and by the way, the picture she chose is one she took of a home being built in Elmendorf at Homewood Place by Flagship Homes, a builder with a good and stable reputation.