It used to be primarily for raising stripers to be stocked in the san fran bay/delta. This was recently stopped because the striped bass population in the bay/delta exceeded what the DFG thinks is healthy for the salmon population (basically a bunch of horse ####, they're pointing fingers in the wrong direction, but I won't go further). Right now I don't know where the money's going. Maybe to stock millerton, san luis, etc...
But I want the striper stamp to stay alive. I'd rather pay the $3.70 a year and demand them to do something with it. Demanding they discontinue the stamp because they aren't using it for plants right now is a good way to make sure they never plant again.