Minimum range

This is likely a common feature of simulation games where long barreled guns can't fire at targets that are closer than the muzzle, thus it is valid and efficient tactic to close in past the muzzle.

In other instances this may be simply self-preservation mechanic where units or weapons refuse to fire if it would hurt themselves or their wielders due to explosions or such. Having mentioned that, this tag is not about minimum safe distance.