Why concierge? There are three probable reasons.
1. Some people travel first class and $400 per night is not out of the norm for them to get one of the best rooms.
2. It can be worth the extra expense. Concierge services vary by resort, but for a family of four to get free breakfast is worth a few bucks. Depending on the resort, the "snacks" served st lunch and dinner can also be a quick meal if you're at the resort. Free snacks and drinks all day also save some bucks with kids. Wine and cheese in later afternoon and drinks and desserts in the evening are also a nice touch for tired adults...especially those who want to sit in a quiet area and visit with friends while the kids watch Disney films on a big screen tv. The staff will also give you a lot of individual attention, answer all your questions about WDW, make PS , buy show tickets and book backstage tours. In some resorts, such as Boardwalk, there are staff members who will contact you in the weeks before your visit to help plan your itinerary and book things in advance.
3. My reason for staying at concierge was that I wanted good rooms and BWI and GF were offering concierge at the same or better price than a regular deluxe room on AP if you asked. AKL was only offering a deal on standard rooms but offered an upgrade to deluxe concierge for a similar rate to a regular deluxe room. Had I been offered deluxe rooms without concierge at a similar savings, I would probably have taken it.