I think a lot of it has to do with going out of your way to drop these heads off, most locations are relatively spread out throughout San Diego. You even said it yourself, " I can try to work it out to pick up the head on my way in to work. No promises though, that's all on my own time and I would't get paid for it..."
Another thing that comes to mind is the stones, people want them as they are looked at as a personal success trophy.
Culture, My in-laws are Filipino and they would shit a brick house if i gave the most sought after part of the fish to some dude who wants do research on it. Asians love the heads for soup man.
Not storm I'm willing to walk through. Others maybe but not me man, sorry.
