Probably. The connections out of SEA aren't that awesome, either- the only 7 day flight SEA-BOS is just the red-eye out of LAX, with 3+ hour layovers, plus a couple of M-F flights. BOS-SEA is better, but not much.

I am guessing that connecting traffic on VX is pretty slim, and that things are point to point, plus you really need more frequencies to make hub/spoke work. This is sort of logical when you realize that B6 and AS fly this route directly for SEA, much like UA and B6 fly this directly for SAN. VX is probably just trying to optimize scheduling for SFO and LAX at this point.