Bodkin arrows were arrows specifically designed to pass through heavy armors. Penetrating the armor only a few centimeters, but many times it was enough to kill someone. Bodkin arrows were easy to pull out and because most of armies have light and medium armors, they weren't used as much.
Full plate armor protects the wearer from sword attacks and classic arrows shot from normal bows ... but all heavy axes, maces, hammers, crossbows and English bows (with bodkin arrows) pass through or destroy it. This type of armor was use in countries, where the sword was used as the main weapon (no axes, hammers,...) and that was reason, why the rich nobles, knights and kings used these armors. Many of them never used their armors in battle, because they just sat on their horses far from the battlefield and never personally joined the battle.