I work primarily with Advaliant, Copeac, and smaller in-house affiliate programs. Oh yeah. And as you know I'm starting to work with CPAE.
It's all the same reason. I trust them. Advaliant in particular almost always exceeds what I ask of them. Copeac is more or less the same. I know either AM will bend over backwards to make shit work for me.
Trust is the major motivating factor for me because an extra dollar or whatever per lead doesn't matter if I know my traffic source is going to leak, or if I'm going to *magically* be competing with their in house team, or if I'm getting leads shaved/scrubbed left and right. Or for that matter if the network is going to be a pain in the ass about paying me.
I like to think it's kind of a mutually beneficial relationship. They know they have more to gain by treating me right on shit because they know it takes a LOT to get me to move my traffic if I trust them, even if another company might outbid them. So because of that, I get treated better than I would at some company that doesn't know me.
Oh yeah. and the in house programs generally suck. But typically there's not as much competition since they probably have at most 50 affiliates. I've actually had issues because some didn't KNOW they had an affiliate program setup(it came default on their software).