I too failed to see the point of 70mm, especially when the shutter opening of my 6x6 cameras is still only 54mm, having 70mm film only means you get more black around the edges (although, to be fair, that might make handling/scanning a bit easier, but it wouldn't fit my enlarger).
Only for RB/RZ67 does it make sense, and only if the film roller goes the 'other' way and you get more shots on the roll.
It only makes sense if the film is cheaper, ie there's a guy selling 100' of Ektachrome (exp 2004) for about $100 on fleabay right now. If that's all it sells for that's gotta work out to the equivalent of a few dollars a roll of 120.
But if you're buying new, like on the Ilford special order (I didn't, but i'm pretty sure there was enough to fulfill), maybe it's worth it to you to shoot old 116/616 cameras. Otherwise, if it's on a hassy, and you're just paying more for extra edges, yeah, I don't see the point.