I develop my own film, rolling onto stainless steel reels. And sometimes it takes a bit to get the film under the clip at the center of the reel and I end up with those small crescents from creasing the film ever so slightly. So for me an inch or more of blank film at the end of the roll is a safety area. Maybe if it wasn't there I'd be much more careful in loading the reel.

I rarely get 120 developed at a lab, but I imagine that machines or such need some handling room at each end of the roll.

So this safety zone at the ends would be my concern. I'm sure the Holga crowd would love the machine marks and such in their frame, but that's not my style.