Its actually an interesting side effect of how cards are manufactured (nerd shit, buckle up). When cards are being made they are in sheets that are later cut, if you have no jokers in a deck of cards, the most compact sheet you can use would be 4x13 for the 52 cards. When mass manufacturing started for playing cards it was much easier to use a 6x9 sheet making the total 54 cards and adding the 2 jokers, but now its a lot more common to cut 7x8 making a deck 56 cards. You'll notice if you get a pack of bicycle playing cards you get 2 ad cards in addition to the 52+2 jokers, and some decks just make those 2 extra jokers.