I'm a very private birther and have never had anyone at my births, except the first when DH called our Bradley instructor b/c he was overwhelmed.
As a birth pro with my last two, I've felt the political game come into play. If I ask one person and not the other, then... or I know too much about the people I'd ask to be at my births. Or we socialize normally and I'm not one to socialize in labor so it would feel awkward. Or I'm not sure I could face them later. Or one is my apprentice and I'm not sure how I'd feel about that relationship after...
So it's always just been me and DH. I've had people on call if I needed them and he called a friend of mine when I asked for drugs in my third labor (baby was born before she could do anything to help). I'm kind of an in-charge person even in labor until I'm not and then, because I'm usually really in-charge, I'm very, very vulnerable and I don't let many people see me like that, so it makes sense that I'd be a lone birther.
I do kinda wish someone had been there for DH at my last birth. I retained the placenta and bled into my uterus. Had to have an "unplanned OR procedure" and two units of blood and left him in the room alone with a baby less than an hour old. I think having someone with him then would have been good. He did fine, though, and even brought tears to the nurse's eyes when he put baby skin-to-skin under a blanket to help her stay warm :).