LAX and SFO are UAL hubs, so a great many SKW UAX flights operate of those airports. SKW (for several reasons) has found it convenient to base the pilots who support those hubs at outstations...that way they are in position to start their day with the early-am flight for pax who need to get to a hub to make a connection. That way SKW doesn't have to get hotels at the outstations.

The reserves are there mostly to cover duty time-outs or mx repo flights, although they could get DH'ed to an outstation for a sick call (the outstations have their own reserves however). Also if you're in the middle of a trip and get sick, most folks will try to make it back to a pilot base before they call in sick (if possible).