Just to throw some extra fuel on the fire...

People brought up the example that tanks can Need on tank gear because, in theory, they need them, right? It's true; I regularly (or used to, anyway) Need lot tank accessories... to level my Goldsmithing desynthesis! Is this an abuse? Maybe. I did it unapologetically and without regret, though. To me, improving my Goldsmith was just as valid a reason for claiming that loot as allowing another person to lot the item to gear up an alt class (or even just trade the item in for GC points).

Materials are the same way. Maybe you can use mats yourself, but that doesn't change the fact that Joe Blackmage over there can sell the mat and use the money earned to improve their own character (or even to buy a mat that THEY can use).

Allowing anyone to lot on mats is fine.