That's not how you shuffle cards though. First you cut the deck, such that the bottom card is somewhere near the middle. Then you split and riffle.

If you do that seven times you get a random deck.

If you do it three times you get a fairly random deck, but you'll get clumps of cards together. That's why casinos usually use three cut/riffle steps, and why you can have an advantage playing with a hand shuffled deck.

It's also why I will never play with a machine shuffled deck. Because those are actually shuffled seven times, and are truly random.