Maybe its because no one wants last years phone in a plastic colored case?? No surprises here.
The number of people who care about tech specifications is dwarfed, massively, by the number of people who buy the phone that looks cool.
This phone is going to be the Christmas present for teenage kids (where $100 in savings means something), the girl who loads all her Ke$ha albums on it immediately and buys the pink one because it looks "hot," etc. None of these people post on MacRumors, none of them are even aware what "last years phone" means, and none of them are waiting up until 3AM to be sure they have the phone on day #1.
Watch where the sales numbers are on December 25th -- guarantee you that the 5c will have lapped the 5s many times over.