If you go to the SAS webpage and make a fake booking (just to get to the passenger details page).
In the drop down menu for e-ticket you have lots of options including:
*Swedish Bankkort
*Swedish Köpkort
*Swedish Sparbankskort
*Booking reference (no card)

And of course all the major CC and FF-card as well as some debit cards.

For people who don't own one single plastic card, irrespective of age or whatever, there is still the option to just get the booking reference without having the booking linked to a card.