Although I now sleep in a hammock when I can (and use a quilt with it) I started using quilts when I was still sleeping on the ground.
I like quilts because I like to sprawl and I can't do that in a bag. (yes, I sprawl in my hammock also).
I like being able to just toss the covers off when I want to get up.
I already have insulation under me so why bother carrying around more insulation I'll just squash when I lie on it?
There is no cold zipper to touch me.