I think dysfunction like you describe comes from organisations that don't value developer opinion. I don't particularly blame some contractors for taking advantage of that and making a living from it, but it reflects the organisation, not the contractors per se.

My last company was like that and contractors played the role of "yes"-person all the time. Where I am now, though is very different. Everyone discusses ideas and decisions are not taken without considering options. Contractors get stuck in with everyone else and don't just shovel bad solutions to problems.