Well, it's all about statistics. If you shuffle a large enough amount of decks, you'll eventually get one which ends up the way it is "supposed" to be (Ordered, that is)
However, since there are 52 cards in a deck (54 with Jokers), simple maths shows you there are 52! ordering possibilities: The first card can be in one of the 52 places, the second anywhere the first isn't (51 places) etc etc.
52! = 80,658,175,170,943,878,571,660,636,856,403,766,975,28 9,505,440,883,277,824, 000,000,000,000
That's a lot. That's more than 80 unvigintillion. Now imagine having the odds of (1):(52!). How often do you think such an orderly shuffle would happen?
I'll tell you what. Even if you'll take a trillion people (1,000,000,000,000) and have every one of them shuffle and check a hundred decks a second - it would still take them more than 25,561,949,410,833,453,309,140,089,008,177,653,221,55 3,370 million years.