People have been trying to predict the future and "tell their fortune", well, forever. Every culture has some sort of divination be it a special person within the society (shamen, priests witches, gypsies, the Pythia of Delphi, psychics, you name it). Just the same, there are all sorts of things, tools that anyone can use to do the same thing. Again, these "oracle tools" (as I like to call them) are ubiquitous and global: Tarot cards, palm lines, rune stones, scrying mirrors, tea leaves, bones, entrails, the list is enormous.
It's no surprise that modern items have been called into use, like our contemporary gaming cards. There are a lot of similarities between the minor arcana portion of the Tarot deck and the playing cards we've all used for poker, bridge and solitaire. After all, Tarot cards were originally a game too.
The fancy name for doing intuitive readings with regular playing cards is "cartomancy". Cartomancy has several advantages. It is an easy way to learn to use cards as a way to access the natural intuition that everyone has. Without the ornate artwork, or the complicated symbolism you see on Tarot cards, modern cards let you keep it all simple. Simplicity embraces all the possibilities. The simplicity of playing cards make them easy for beginners to use, at the same time it is unrestricted...it lifts the boundaries and lets an experienced reader shine too.
Simple is neutral. Modern cards don't have the emotional and cultural baggage that tarot cards can have. Some people are put off by Tarot's reputation of being "occult". Others find the religious imagery on older decks uncomfortable. Neither of these are a problem with playing cards, making them comfortable and accessible to a wide range of people.There are no scary pictures in the game deck, so they are nice for a first reading or anyone who is feeling timid about the whole reading process. I always keep a game deck on hand for anyone who would rather have a cartomancy reading instead of a tarot reading. Since I work only with entertainment and advice (never predictions) anyway, the two are completely interchangeable. Tarot went from game to oracle, and so have our modern playing cards.