I'd say it's still the case. Off the top of my head, we have chains like In N Out, Fat Burger (Magic Johnson owned some of this, not sure if he still does), Tommy's, Jim's and Astro Burger. There are even little chains with names like Tom's, Tomas, etc. playing off the popularity of Tommy's. There's also Carl's Jr. but it fits the model of the national chains. Virtually every mid range and below restaurant offers burgers. As to why this is, I'm guessing but possibilities are: low paid immigrant/illegal labor, family businesses run by hardworking families (often immigrants), undeclared cash receipts, a populace that likes burgers and tacos and chicken, etc. eaten on the run. I don't know if this is unique to LA (when I was growing up in Texas, there were numerous small chains but that was years ago), but generally these folks make better burgers than McD's etc. Let's not forget the original McD's was a family run shop in, I think, Downey or El Monte or somewhere around here. For reasons that continue to escape me, Fat Burger does not make it in the LA Zagat guide whereas In N Out, Astro and Tommy's do.