Not a D&D thing? I mean did any of you see the artwork for 2nd edition AD&D?
In all seriousness, it makes sense from a mage perspective where Magic sees you through, less so for proper armpit, apart from magical armpit because again, magic.
Do I need it? No. If done with humour or in moderation, sure, why not. Certainly wouldn’t want it as main design philosophy and I’m pretty sure we are safe from that.