As a general, or a homeowner, I want to treat my subs as humans, and I want to be nice. I keep lots of pop on hand, order pizzas delivered, etc. I am polite, I joke around with them, and I almost never get into a shouting match with them. The construction world is very very small, and I have to maintain relationships with people, no matter how insignificant I might think they are, because I never know if they won't be the only one available for my next job with my favorite client.
There are a couple areas I don't mess around with, and my subs will be fired on the spot. One is dishonesty, and the other is drinking on the job.
Beyond that, everything is politics, back scratching, etc. There's a saying here in some parts of Seattle, and that is "Never piss off the barista (espresso maker person), you don't know what they won't do to your cup of coffee." Same thing with subs.