Because he's going on a 6 month loan. We did not sell him like we sold Mata. Selling a legend to a direct rival now that would be preposterous. It was best decided that Lampard should go, because he still want to remain competitive and at Chelsea we have other players that will take his spot and can't promise him first team. So he move to MLS to play regular, at City he will not play regular....well we will have to see about that.