There is a lot of symbolism there, but there are some practicalities to it. A handgun is generally a defensive weapon or only a last ditch offensive one. Rifles/carbines/SMGs do the "work". Officers are commanding, not doing the grunt work, so why do they need anything other than a handgun? Now it does make a lot of sense to equip infantry with a handgun for backup, but that is an awful lot of handguns you need to produce for little gain.On pistols, one thing to keep in mind that in Europe and the Russia/the USSR, pistols were (and still are to a great degree) more a badge of rank than a practical weapon. I think it's kind of a throwback to the old days when swords were only worn by nobility. Peasants were pikemen, but the nobles who lead them carried swords. That continued for a while even after swords ceased to be practical on the battlefield...