Actually I was talking about the organization that represents low-paid university workers, like janitors and cafeteria workers. I reworded my post to clarify.
Graduate students are a whole 'nother basket of beans.
farm workers have the UFW but being a farm worker remains one of the most intensely miserable jobs in the US, with constant rule-breaking by the employers, and a lot of unrepresented workers.
I don't think it is fair to blame the large number of unrepresented workers on the union itself. I'm sure the UFW wants to increase their membership past the paltry ~5,000 it has.
Graduate students are a whole 'nother basket of beans.