This is true, but there's still the problem of how things are distributed within the collective groups.

When the labor market gets competitive, you start to see long probationary periods, two-tier pay and benefit scales, hiring people on as casuals instead of permanent members, and other bargaining concessions that end up favoring some union members over others. I know some unions over the last few years have managed to fight against two-tier systems, but if there's any sort of serious economic downturn I'd expect them to become commonplace again.

I'm curious to see if they can come up with a way to organize that works for everyone, or if it'll end up as something like the Longshoreman's union: a fantastic deal, provided you won the lottery to get in and then stuck around long enough to be a permanent member.