|Actually, I'd be surprised if 10/2 was used in 120V circuits at all.
Very common in the recreational vehicle world. Let me rephrase...120V,
30A circuits are very common in the RV world. (What wire size they use
is unknown) Most RV parks provide 30A hookups; with some supplying
50A circuits for "big rigs", those with dual A/C, washer/driers, etc.