I had a very smart Captain explain it to me. When our Fa's were trying to unionize he told all of them "hey you don't want to do that Delta has always taken care of you" (which they do pretty well for the FA's). When I asked him why he didn't want them to unionized he summed it up with this:

"Do you want them to have a right to strike? A lot, not all, but a lot of their incomes are secondary in a household. Additionally they can readily replace that income with a lot of other jobs outside the industry. Now how easy is it going to be for you to find a six figure job when the airline gets shutdown due to an FA strike or slowdown? Not as easy as it will be for them to replace their income."

Ever since then I don't promote unionism to FA's.