Analysis of Greek prehistoric combat in full body armour

Spears are meant to keep the enemy at a distance. Aiming for the foot would require some reaching, putting you in significant danger of counter attack. Armies lined up in row and each man covered the man to his right so reaching in battle would be a risky maneuver.

As for protection against arrows only requires a thin layer of armor to deflect, and that armor is best located above the knee since arrows come from above. Alexander’s phalanx did not utilize foot or leg protection except for the most prestigious officers. Their thin shields were wide enough to cover their body, and it was noted that a phalanx with their spears raised, could scatter a volley of arrows along the spear shafts.

Keep in mind all of this equipment needs to be packed and marched long distances, in the summer heat since armies did not campaign in the winter due to challenges with provisioning a sizable armies in wintertime. The wealthy elite could have baggage trains to carry superfluous equipment, but the bulk of any army marched on their own two legs and carried everything they went to war with on their backs.