Well, the problem in discussing such things in the net is that most people discussing here have no, or very limited, real experience with the whole thing. They think that playing an online slave/master is something similar to the real thing.
As for what drives people...it's a fault to generalize there. See, I have been doing BDSM stuff now for over a decade, have met many many people. And not two of them are the same, be it what they like or what motivates them.
For me, having a submissive is owning her. Yet, I have heard no complaints so far

It is a gift the submissve presents to me and shall be properly valued.
Trust is important, though, on both sides. I would never tie up a sub I dont trust.
Cheers
FF
There are 10 kind of people in the world.
Those who understand binary numeral system, and those who don't.