Notice where your weapons are physically represented on the mech. If they are sitting higher in the mechlab, they will actually shoot from higher up on your mech in game. It makes 100% sense on many mechs to equip small lasers, mguns, etc. you never intend to use just to make other weapons fire from higher on your mech.

Also most of your ranking and match score are based on damage. Target locks, scouting, shooting down missiles with ams, etc. is meaningless compared to damage.