Calling baby diapers as diapers and adult diapers briefs doesn't really bother me in the least. I can certainly understand that incontinent adults would not want to associate diapers with being a baby, so I am assuming that would be one of the reasons for the different terminology.
Also, there are different types of adult absorbent products, whereas for babies, they are all diapers. Adults have a wide selection of tape on briefs, pull ups, belted undergarments, guards, pads, etc, so most of them could be referred to as "diapers" but each has their own description, at least that's how I see it.
And on the topic of Spades... the Ace has spoken.