It's realistic and fun. Players can level up their Pickpocketing skill by robbing other players so we should be able to level up our weapon skill by shooting another players . Additionally, players sometimes don't level up their skills in the shooting range because it's a boring and repetitive task. This is how it works in the base game, so it makes sense.
Duels and events should not count as a way to level up the skill to prevent abuse. The leveling should be slower than in the shooting range to still encourage players to level up their skills there, as it's faster than just leveling up by shooting other players
