I think it's tied to swing speed. I've always used drivers set at a slightly higher loft as to get a bit more carry sends it further for me. My swing isn't the fastest, so if I was to use a 9° for example, I think it would just shoot out low, hit the ground earlier and only a small amount of extra roll wouldn't be enough to compensate, ergo the higher loft goes further for me.
I like to use higher loft as I feel can get more carry and hit straighter balls.
If a ball spins on a single axis through it's centre, it will always have "backspin" and a degree of sidespin. The more the effect of backspin on it the less the effect of the side spin.
So if you hit a low degree driver like 9 or less, the backspin will be low and the effect of the side spin will be greater. This is going to cause too many hooks and slices.