As Walt intimated, the CA fair is an apa/aba sponsored event. Not all fairs are. In New England states there are multiple large ag fairs per state, but each only has one that is sponsored by an APA/ABA club, which then uses the fair ground for an APA/ABA show. The difference in the quality of bird and knowledgeableness of owner is outstanding. If a given fair is not an APA/ABA sponsored event there is little reason for a serious breeder to attend. ON the one hand there are no points, on the other, his or her friends aren't there, and lastly going to any show stresses birds, so serious breeder is not going to waste a move on a non-APA/ABA event.
Then again, we're talking about mites and lice here. These are pests but not the end of the world. If I brought home mites or lice from a show, I'd be ******, but that's about it. It's not really a big deal aside from being a grand annoyance. Now, a disease, that's different story.