Maybe you don't listen on port 80 but I can imagine a standard web server using Let's Encrypt, for example, that could suffer from a user leaking credentials by inadvertently using HTTP rather than HTTPS.

I have to look into some protections to this. I recently did a project and used Basic Auth for expediency thinking that later I would replace with a "proper" auth form. My theory was that this was better because sending cookies is based on the protocol also not just the domain.