The concept behind a clean slate is rather simple. For instance, the metamorphic rock doesn't necessarily have to be shiny and sparkling to start with. Some stains are permanent, and it doesn't really matter how many hours you spend on your knees, with a bucket of water by your side and a scrub brush in your hand, because in the end, even though you manage to visibly hide them, deep down you know they're still there. You know you're not fooling anybody, except maybe yourself. And that, truth be told, is not such a bad thing. It keeps you grounded. Maybe even hopeful.
When you're born, when you're still curious to the colourful halo singing lullabies that's surrounding your head, decisions are made for you. You are given a name, regardless of whether you like it or not. You are forced to suckle this white liquid, which you later learn is called milk, out of this weirdly shaped balloon, even though, if it were up to you, you would refuse to have anything to do with it. Simply put, you are imprisoned in a cute little body and you have no say in what happens to it whatsoever. The slate is tainted by people other than yourself.
But then, as you grow older, you assume full responsibility. The downfalls, the mistakes, the victories, they're all up to you. Every experience you have ever lived through, good or bad, has made you who you are. And yes, you can clean the slate and start fresh (or almost), but the stains are still going to be there, as a reminder of who you were and where you came from. So what you can do, instead of cleaning your old slate Cinderella style, is get a new one. The purchase is expensive and non-refundable, and it cannot be exchanged under any circumstances.
The newly purchased slate, however, is also pure and unstained.
Not to mention fake.