Bluetooth for Cordless Phones

In general, I don't understand why cordless phones haven't progressed to have more of the quality/qualities of cell phones. In particularly, I am baffled as to why there is almost no bluetooth on cordless phones. We all love our bluetooth headsets, wouldn't it be nice to be able to use them at home, with our cordless phones? (I know, there are bluetooth pairing complications that would make this not as smooth as we would like. Still.)