If each of the blues didn't cover their whole state, they'd have to change their name to Blue Cross Blue Shield of Portions of Texas
There's multiple blues in PA and NY. Not sure on other states.
And Weho...its also based on network. There has to be X doc/facilites vs the population to offer an MAPD or HMO in that county.
For example...Rockwall County can't offer Scott and White. Denton county has similar issues.