Because nipple wrenches are only made in four sizes: small revolver, large revolver, rifle and musket. Or whatever the latest marketing scheme says it wants.
The No. 10 and No. 11 designations used to identify cap sizes, and by association nipple sizes, are actually meaningless. There is no standard "No. 10" or "No. 11" cap size, and to carry that over to nipple sizes like Treso does is even less useful.
I recommend the ML063 double ended, hardened nipple wrench for revolvers from
RMC-OxYoke. Arcticap turned me on to this one and so far, it's the best I've found.
There is also a small ratchet wrench with inserts that fit large and small revolver nipples and musket nipples that works extremely well. It's sold by
The Possible Shop; they call the bits "for No. 11 nipples" which really means large revolver and rifle, "for musket nipples" and "for cap and ball revolvers" which means small revolvers. I've had no problems with it and actually solved a couple of stubborn nipples that nothing else would touch.