Good point. There are still quite a few DME arc approaches here in the Pacific Northwest, but even if you aren't flying a DME arc, you might want the 10 nm ring displayed so you complete your procedure turn within that distance.
It would be nice if you could touch/select the relevant VOR, then get a menu that asks what radial(s) you want displayed and an option to display an arc of x miles.
I know that some on this forum have said that the iFly is not intended to be relied on for IFR flight and I agree. However, in a typical approach, I may have the #1 VOR tuned to the ILS/LOC and the #2 set up for the missed. Having the iFly show one or more radials that define step-down fixes would help.