Why did Greek Equipment get lighter?

[Geoffrey S]

But it is incredibly easy to give a guy a spear and shield, then train him with a militia to form a wall of spears, and that with the most primitive technology. Essentially, there were already predecessors that later led to hoplite warfare among the infantry... Wealthy citizens, and even the aristocracy, would gradually fight on foot as elite heavy infantry. That would lead to the technical and tactical upgrades leading to late hoplite warfare.

At the risk of sounding obvious, not all spear-armed and shieldwall-forming troops are hoplites, or even necessarily predecessors thereof. Hoplites were also very much a product of social and economic forces.

[Leão magno]

This happens until our days, foot soldiers are always getting more specialized and lighter in equipment and capable to deliver the same amount of destruction as the earlier heavier units