Because people are pussies who are afraid of risk.

At the moment, I still appreciate the idea of unionizing to improve the voice of non-management in certain decisionmaking, and especially for salaried workers, I think a group mentality making sure people aren't getting abused on hours is great!

But is it worth the risk to talk about it? After all, I've been told you might get fired by management! Oh my, well, I'd have to elect members, and sign papers... let's just keep working.