Yeah I don't blame them for not going to Mexico. I know I'd be a little nervous. LA and San Diego are too far away for Alaska. I would say San Francisco is the farthest south to cruise to Alaska, any farther south is too far away (just like much farther north than New York is too far away from the Caribbean).
If they could build faster ships they could offer weekly trips to Hawaii from SoCal. But right now ships don't go nearly fast enough.
Past Cruises (all except one from NYC)
Carnival Triumph to Canada: August 1999
Carnival Victory to Canada: July 2000
Celebrity Zenith to Bermuda: July 2001 AND July 2002
Celebrity Galaxy to Caribbean (from Baltimore): July 2003
Voyager of the Seas to Caribbean: July 2004
Crown Princess to Caribbean: July 2006
Carnival Victory to Canada: August 2007
Carnival Miracle to Caribbean: May 2008
Staten Island Ferry, I mean what else in NYC is free?