I've wondered that myself because California has had some very talented players.
I guess that's why the other teams' net result from open tryouts is usually better than ours. I think a few of our bumbling idiots on our PR last year came from open tryouts. Generally, though, these guys who show up at the open tryouts consist of less athletically developed or less skilled players and they go the these open tryouts out of desperation because the NFL isn't "remotely" interested in their antics to play football nor does the NFL waste their time on them.
I think the NFL has had a few tryouts, but by invitation only and/or only when a specific position is needed.
The "recipe" for our winning team has come from the "ingredients" (experience) of our real players, not from some of those picked up from some open tryout. And I'm pretty sure some of the other teams have had better luck with the results of their open tryouts - maybe because they were in California. I really don't see a lot of reason for these open tryouts anyway.
Not sure about Pierce - would make sense that he was at CA tryout though since he went to NM State, but Elimimian was picked up at tryout in Los Angeles.