I tend to do backward rolls pretty often when thrown from iriminage variants. Depends very much on the energy and direction of the throw -- it sometimes just feels more "natural" to me. It's definitely a habit rather than a choice though, and I'm trying to get rid of it.
Heck, I've even done a "shoulder stand" (one shoulder on the floor, rest of the body straight upwards) for a few seconds while trying to decide which kind of roll/fall to do. Not something I want to have as ingrained reaction