Playing into justifying "hi cap" mags is the point - a 30 rounder is standard. Ten is a low capacity hunting magazine.
Capacity isn't a real issue anyway - one of the Columbine shooters had a weapon with 17 TEN round magazines, and it didn't seem to impede him any. The Newton shooter changed mags repeatedly, leaving partially filled ones scattered thru out the building.
If someone asks why I need a "hi cap" mag, I'm now likely to ask why they need a 24 pack of beer, or a carton of cigarettes, or more than ten gallons of gas.
The concept of magazine capacity is a deliberate ploy to suck you into bargaining about what you can get by with - any limitation is exactly that, and a victory for them.