Why make Priority weapons when the system already does a lot?

[Chardrizard]

Before you do the run everyone in the party says what weapon they want so if that weapon drops it doesn't matter who it drops to they pass it to the person that called that weapon.

That is the way most pick up group does things because while the system does the randomized system itself, it doesn't know what jobs you want to gear up. Does the system knows you want WHM cane? i dont think so.

If there is no clear loot rules, you might not even get WHM cane at all because someone else that doesnt even want them might keep getting'em and decide to just sell it after.