It is kind of an inside joke (not the best description, but close enough). People in the military know how shitty some of their gear is. Military grade used in marketing only makes people who don’t know think it is tough shit. Military folk know it means nothing.

Commercial still has to be somewhat good (in general) to stay in business. Military suppliers just need to supply Trump with pre-teens so they can cut even more corners.

"military grade" sounds way cooler to idiots than "commercial grade"

Private buyers can choose from any number of manufacturers, from shit to actually good stuff. Military is always the lowest bidder.