Celebrity used to do this way back in '09. I spoke to a head marketing guy on a cruise in '17 about this ..asking why there weren't more west coast sailings and why use LA versus SD which is such a nicer, easier to port to access. He told me that X didn't think they would get enough business on west coast sailings!! I told him based on comments on CC i thought they would have plenty of bookings. Looks like they have changed their minds..at least somewhat.
HAL is still sailing from SD to MX, HI and Pacific Coastal..also some further out to Tahiti from SD.