Many games have Melee, Firearms, Unarmed, Explosives, and you can win any fight if you have at least one. Might as well just have Combat.
Wrrrrrrong~ You are speaking ,like a combat noob.
The purpose of dividing into Melee, Firearms, Unarmed, Explosives, etc a variety of different Combat skill is to serve defining different combat tactic/style.
Melee? Up close combat has different requirement compared to range.
Unarmed? Using tool to hit instead of feeling fist on flesh is a different beast altogether. The former rely on finding better combat tool while the latter just need to increase skill. A 120 Unarmed fighter is very different than a 120 melee combat fighter in early stage, middle stage, and end stage of game. The win/lose depend on whether melee fighter can find better weapons.
Firearms? Obviously range combat is different than melee combat. Plus you can have many different type of guns which is an important aspect of game.
Explosives? Its role of AoE short-range weapon can have some important effect in game aside from combat.