From a game-design perspective, I was wondering what the mechanic of manually picking up items off the ground does for the player. Keep in mind that items that fall on the ground can most likely be put into one of two groups:
Equipment Items: depending on the character the player is creating, the majority of these items might be ignored and left on the ground. Players will only pick up the ones that they want to "spend" inventory space and time (by clicking and eventually having to go back to town) on.
Consumables: gold, gems, crafting materials, etc - which players generally always want to pick up and sometimes don't take up inventory space.
While I can see that making players choose which items to pick up is an interesting "collecting" mechanic for the Equipment group, why make the "Consumable" group require manual picking up as well?
Examples of games which do this: (most diablo-esque dungeon crawlers)