Familiar Ground

In D&D, each part of the body can only make use of the effects of one magical clothing at a time (one magic cape, one pair of magic gloves, one magic hat, etc), and there were only a dozen or so standard “body slots”.

That made non-standard “body-slot” items valuable because it meant that the character had access to one more magical item that a typical adventurer doesn’t.  In the Living Greyhawk campaign for instance, a magical undershirt that can be worn underneath regular armor and enchanted for magic resistance was available in one specific adventure module, and people went to great lengths to be able to get it (some travelled hundreds of miles! – and no, that wasn’t me).

Don’t even get me started on what stupid enchantments Elminster had on his underwear.