I think you summed it up. Competition. It's like why does DL gouge for non-stops out of MSP to almost everywhere except PHX, DEN, MKE, and ORD; primarily because corporate MN will may for it and there's no competition.

I've done MSP-JFK-SFO numerous times for work (we use it as an excuse to prepare for meetings and we can usually get more work done in the air) and the DL transcon FA's are the best FC FA's in the DL network. I even mentioned it once to an FA how much better they were than their counterparts and was told "If we acted like an MSP or ATL based crew, everyone would fly AA or UA's p.s. and I wouldn't have a job."

CO's lackluster Y/transcon product is primarily due to lack of competition. We have an office in East Rutherford, NJ and the transcon flight length would qualify them for booking it in F/C, on ex-EWR, yet many of them go to JFK for UA or DL (and sometimes they can book AA) as they say the service improvement justifies the trek over to JFK.