Walking through the alleys of the docks district of town, you hear an old, mad beggar calling out for alms. He claims to be a god, cast out from heaven and stripped of his powers. The party passes, tossing a few coppers to him. In thanking them, the madman refers to incidents in their childhood or distant past which would have been all but impossible for him to know.
Tarot Cards are used by Magic folks to predict the future (cartomancy). Since the present becomes the future through the interplay of elementally alligned forces, the tumble of cards can give clues to the way the pattern of elements will be in the future.
This means a wizard will have a deck of cards with them. Since cards were used to train wizards in legerdemain, Since they have cards with them, they frequently know how to use them. Guild magic users often have a knack for fancy shuffles, palming cards, and a variety of card tricks and games.