I am a native of Southern California . In the 60s and early 70s there quite a number of interesting branchlines on the verge of abandonment ,but no group or organization stepped up to the plate . At the time most tourist steam operations were on existing roads ,simply because the infrastructure and equipment was already in place . The Cal Western ,Sierra ,and Westside were examples of that.Of course ,these lines were in Northern Cal . There quite a number of privately owned locomotives in the LA and San Diego area . Why didn't a tourist shortline happen ? Real estate was pricey . There was an early awareness of air pollution there.Most railfan ventures seemed woefully underfunded ,like the California Narrow Gauge Rail Museum and the Puddingstone Reservoir venture . Big money stayed away from such ventures ,and funding , private or public was (hard to believe) almost impossible to get at the time . It might be noted that none of the railfan ventures I heard of had coherent or comprehensive master plans .There was an attitude of "if we build it they will come" . As Brian pointed out ,the region has lots of attractions competing for the public's attention in a crowded media market. Also railfans in the area had a bad reputation for their unreasonableness and abrasiveness . They were loathed by the three very busy mainlines who served the region .
For many years the best a local fan could do is a trip to Knott's to see a nice collection of stuff in a very claustophobic and noisy environment. After some rough going at the beginning ,the Orange Empire Museum got a very unique 2-6-2 going ,as well as Ward Kimball's magnificent collection of Far West narrow gauge ,conserved in a large metal building .Orange Empire Museum is a "must see" for several reasons .Located in a beautiful valley in the Coast Range ,it has an extensive collection of Pacific Electric equipment ,including a sentimental favorite ,the narrow-gauge streecars of LA Railways ,which yours truly had the good fortune to ride as a boy .