I do that, too. Picking up only between rings, you see. I'm not entirely sure why, but here's a theory
Phone rings. It makes a loud noise, and shakes. I see that the handle shakes, too, so logically I assume it makes loud noise as well. Of course I won't pick up the damn handle and put it in my ear. It'd make noises in my ear! And believe me, some phones are painful enough to listen from a distance. So, I wait until it stops making noises.
As for b_o_leary's comment, well, at least here in Finland the dead line makes constant beeeeeeeeeeeeeeeeee[p] (it never ends so there is no 'p'), so you'd have to be really dumb to say 'Hello?' to that...