Let me see if I can satisfy AdrianaAurora's request for more psychological insight...
Yes I am also the sort of person who naturally tends to organise and take charge and stuff, and my professional life gives me an opportunity to do all that, but personally I don't think that side of me gives much of an insight into why I get off on being a Dom. I think there are a lot darker and deeper things going on than the fact that I'm a good, well, manager.
That view may derive simply from the fact that I'm an unreconstructed Freudian prone to self-analysis, but I don't think that these 'management' skills are coming from the same part of me that enjoys D/s play. In fact, one of the reasons I think I am a good leader in my professional life is that I don't boss people around.
So why do I want to be a Dom then? Well, who knows for sure. Maybe I'm the last to really know. But I can say that one of the things that I find important about play is that it allows both Doms and subs to open up and accept each other - eccentricities, perversities and all.
And speaking more broadly, if one were to generalise a primary motivator underlying the whole Dom personality type, one such factor could be a general urge and need for being in control. And why might someone feel the need to be in control all the time? Possibly because somewhere deep, deep inside they don't feel very much in control at all?