If you need heirlooms your main is much more suitable for it, as he gets more XP for it. Once you have all your heirlooms you can start going for lvl 34.
Indeed this restriction helps perhaps, but I don't know if so many players would actually behave this way. Playing the other chars just for the sake of farming an item that is supposed for your main who is supposed to be the character that grants you the most fun seems somewhat weird to me