Can't play demo without logging in.

I was going to play demo, but there is no Play Demo button. It would be better if I was able to play demo even if I am logged out.

What I expected to happen was...:

I could freely play demo even if I'm logged out.

What actually happened was...:

Instead, there is no Play Demo button on the login page.

Steps to Reproduce:
1. Make sure you have the launcher installed.
2. Make sure you are logged out.
3. Notice that Play Demo button is missing on the login page. How can I play demo now if I cannot register the Mojang account?