Actually you want to build boats where the air is dry and warm most of the time and there is no need for a climate controlled laminate room. You also want to be near the raw materials manufacturers so that inbound freight doesn't kill your bottom line:

Why they are based in California

Resins: Distributor in Los Angeles
Gelcoat: Distributor in Los Angeles
Aluminum: Extruder and foundry right here
Machine shops: Thousand of them for defense industry
Cordage: Yale distributor is right down the street
Coregated packaging: Manufacturer is here in LA
Foam core: Distributor is here in Los Angeles
Technical: Morrelli and Melvin are just a few minutes away
Parent company : For Perfromance having Catalina Yachts up the street is more cost effective and offers a better level of control.
Sailmakers: Ullman sails and Elliot Pattison are just minutes away from Perfromance which is helpful for battens and sails.

Freight: Los Angeles is the least expensive port in the US (Long Beach also) to ship to Europe. (Yes, even less expensive than East coast ports.

That is why Hobie and Perfromance remain here in California. That and the owners and managers prefer to live here. :-)