I've had a couple of engagements that went well. And I've been invited to bid on some team engagements that appeared to be well defined, well managed, and well structured. But the customer "required" 40 hr/week and paid "okay", but not well enough to suck up 40 hours of my week. I would have considered it if it had been deliverable-based rather than time-based.

But, as the other commenters have stated, most of the jobs pay too little, require immediate turnaround and/or have initial scopes which turn out to be poorly though-out.