I think that one of the big selling points of the belt (or many other infinite use items) is that it lessens the need for paperwork. You no longer have to keep track of how many wands/potions you use, or how many were purchased. That is a very nice meta-benefit.
The belts can be used by anyone, can be used to heal other people, can be used to harm undead. This is the item you want when the cleric is at -1 hp and dropping.