Do you understand the benefits of a union?
Classically speaking, unions existed to drive up benefits through threat of strikes or walkouts. In the 20's and 30's, unions were responsible for the 40 hours workweek, Saturdays off, and a living wage -- by preventing things like random firings and unpaid work (see 80 hour work weeks in the game industry).
To be clear, if individuals were better at negotiating wages, we'd see a rise in salary in the field, but according to statistics this is quite simply not the case. "Ah, but salary went up from 80K to over 100K you say", to which I agree, but if you adjust for inflation, you'll see that that $80K in 2004 is equivalent to $100K in 2014 (26.1%). In the same period, the tech heavy Nasdaq grew 143%. While some of this can be attributed to there being more people employed in the field, I doubt there 2.5x more CS graduates than there were ten years ago.
So while pay is still decent, there's still no rise in salary despite what many consider an obvious shortage in the field. If more CS majors studied those useless fields like "history", we'd have a union and there wouldn't be a bunch of indentured servants known as H1Bs driving wages down (by artificially inflating the labor pool with people who can't quit).