Note the falx damaging the Roman shield at center-right - the penetrative power (and reach) of the falx was so great that the Roman legions temporarily uparmored themselves for operations in Dacia during the Roman-Dacian Wars, including ridged helmets and armguards to protect themselves.

Those pieces were largely discarded after the war as unnecessary weight (and probably as an unnecessary expense too), but against the dreaded Dacian falx, every protection was needed!