UAL: They could but California in general, and LAF and SFO in particular, have full-on socialist labor laws. For this reason alone, SKW keeps as many crews out of Cali as possible, and the ones that are based there are mostly in more conservative rural areas. This is why SLC crews get to visit Cali so often...

DAL: Due to scope language in their UAL contract, SKW cannot operate a DAL base at any United hub (LAX & SFO).