I wouldn't call it less practical though:
"There was also a party of slaves training to be gladiators. Completely encased in iron in the national fashion, these crupellarii, as they were called, were too clumsy for offensive purposes but impregnable in defence…the infantry made a frontal attack. The Gallic flanks were driven in. The iron-clad contingent caused some delay as their casing resisted javelins and swords. However, the Romans used axes and mattocks and struck at their plating and its wearers like men demolishing a wall. Others knocked down the immobile gladiators with poles and pitchforks , and, lacking the power to rise, they were left for dead." Tacitus, Annales, III 43
As you can see, "iron-clad" armor of that time didn't seem to provide superior protection, while superior mobility was an important factor to consider.