Because when making pastry, violence is always the first resort.
There are also plenty of pictures:
Every laminated dough, be it puff pastry, croissant, flaky pastry or Danish, begins its life as a thick slab of butter encased in a dough "envelope". This 3-layer dough-butter-dough package is then flattened and folded however many times it takes to get the number of layers the maker is after. A folded flaky pastry for say, a galette, can have as few as 27 layers. Croissants often have 81, Danish 243, and puff pastry can have as many as 2187 (though I prefer the less flaky version of 729).