All the windows in Cinderella's Castle suite are stained glass. This is partly because it fits with the theming (a guest suite in a castle), and partly for practical reasons. At night, the lights in the Magic Kingdom are turned up, and nightly maintenance is performed on the theme park as surfaces are scrubbed and repainted. In order to preserve the magic, the view from the windows is restricted to Fantasyland.
My first thought was, "How do you see the fireworks from here?" Although you can see them through the windows, the guest suite family also has VIP fireworks seating just outside.
