Tarot is fun. Suspending disbelief for a little bit and letting the reader take you through some mystical mumbo jumbo is neat. Every good tarot reader I've known was also a writer of fiction, it's a neat way to brush up on impromptu storytelling and weaving yarns. A good tarot reader wouldn't even need the deck, but it's an important part of the suspension of disbelief.
Having more than one deck unless you're a fulltime pro is absolutely pointless. It's like buying wands without learning sleight of hand and expecting rabbits to pop out of hats all on their own.