Always on their arse. My brother is building a spec house (to sell when finished) and it's a non stop get your ***** straight, and be done already deal.
When he was building for other than himself, it was paramount to hold onto the crews that were good. They did get kickbacks, but I'm not sure how lucrative.
With other run of the mill hires it was different. If you want work next week, get my stuff done pronto. He got an award once for fastest ever completion of a home when he built for MHI. IIRC, it was 68 days.