Why did Ray Bradbury use the idea of book burning in his novel Fahrenheit 451?

Fahrenheit 451 is the temperature at which paper burns.

If Bradbury hadn't put book burning in the book it wouldn't have any subject matter, there wouldn't be a book at all - you would have effectively burnt 'Fahrenheit 451'.

Basically Ray Bradbury loves books and he's making a point about how important literature is for the imagination and freedom of expression.