It's encrypted by default. I agree that having no option to send unencrypted messages would increase security somewhat, but the unsophisticated user can always

It's encrypted by default. I agree that having no option to send unencrypted messages would increase security somewhat, but the unsophisticated user can always be tricked into sending an unencrypted message. They will just use a different app if something doesn't work. Not really fixable on the application level.