The first time you read Harry Potter, you were in awe. You couldn’t put it down. You wanted to read it over and over. You wanted to live in that world. Harry, Ron, and Hermione became three of your best friends. You knew that they would stay with you until YOUR very end, and you anxiously awaited your Hogwarts letter at age 11. It never came.
The truth is, JK Rowling is a Squib. Yes, she knows all the secrets of the magical world, and yet is she is unable to use any of them. She was excluded by the wizarding world, and yet she didn’t quite fit in with Muggles either. Perhaps it was revenge, and perhaps it was just an attempt to do something for conformity- (and I tell you now, I love JKR like crazy)- but she wrote seven books revealing the well-kept secrets of Hogwarts, and the rest of the magic that she has shown us exists.
She had no Muggle money, and so she started writing on napkins- she was brave, and she was determined, and yet she had completely breached the Statute of Secrecy, which- when tried by the Ministry- it was found that as a Squib there was no specific law, and they were unable to take her to Azkaban.
Well, JK Rowling was a great success in the Muggle World, but wizards were in great danger. Now that their existence had been made known, they would have to find some way of convincing Muggles that they were merely fiction. They sealed the platform at 9 and 3/4. They changed which bricks you had to tap in order to get into Diagon Alley. The biggest change, though, was that they tried to completely separate themselves from the Muggle world.
Muggle borns no longer were accepted into Hogwarts: it was not that they didn’t want to teach these young witches and wizards, it was just that they couldn’t risk this contact in case somebody else decided to alert the Muggle government, press, etc.: it was just too dangerous, and so our Hogwarts letters never came.
The ministry is still keeping track of all the Muggle born witches and wizards throughout the world, though, in the hopes that they will one day find a safe way to admit them into the magical world. Tumblr was created to keep tabs on us, that way, they can track our progress and invite us into the wizarding world- albeit a few years late- but when it is finally safe to do so.
So don’t lose heart: even though age 11 has come and gone, your invitation to the magical world is yet to come.