You are right!
That`s why members asia have membership card says access to DeltaSkyClub and affiliated louges.
But recently I traveled on CI flight and I present my Delta PM card for CI dynasty lounge access but refused due I am not holding SkyClub membership card, so I present my NW Platinum Elite card instead and CI agent accepted.
I called Delta to clarify and I was infromed that ffective March 1st 2010, All PM must travel international to gain SkyClub access with PM card otherwise lounge membership card must be presented at lounge reception.
So that is the reason why Delta mails this SkyClub membership card.
F.Y.I. GM PM DM cards are only frequent flyer program card, it is definitely not lounge membership card.
Delta has adopted the NW rule for its FFP so Gold Platinum and Diamond members are now given complimentary lounge membership. Of couorse FFP membership and lounge membership are two different thing.