Why Are Playing Cards The Devils?

Playing cards are not anymore the devil's than a guitar is. Music can be used for good or bad, as can anything else.
Cards faced many ordinances back as far as the late 1300's because of their gambling uses.
If you go back about four generations, cards were synonymous with gambling, so they were considered taboo even if used for other purposes.the next generation grew up being told they were the devil's tools, and many just accepted those words at face value, without questioning why. (much the same way biases and prejudices are cultivated)
Then the next generation, when asked why they were bad could only respond "because I said so".
Go ahead and play a game of Hearts or 500, keep your money in your pocket, and have a good time.