> It's much more efficient to find the few people who actually have that skill and let them do it for the group
And human nature being what it is, why won't those few people negotiate better deals for themselves while keeping peanuts for the rest? (see: class action layers, bosses of Unions etc).
For the same reason any similar arrangement holds: if it gets bad enough, the torches and pitchforks come out and the group finds themselves a new negotiator.
