I write fiction. Some people write music. Others make movies. There are different ways to express what's in our heads.
But that's not the whole explanation.
When two people fall in love, they, too are creating something out of nothing. One moment, they're two separate people. The next--they're in the presence of that incredible power called love. They just created something out of nothing.
When an artist creates, the work is incomplete until it's shared. When you hear a piece of music or view a painting or read a novel, the moment where you "get it"--that's where the "something" happens. Without an audience, the artist isn't finished.