It's again a user expectation problem. What if you connect to a web site for the first time while on a rogue public network? If users expect to be "safe" when

It's again a user expectation problem. What if you connect to a web site for the first time while on a rogue public network? If users expect to be "safe" when on a secure site, without them understanding intricacies of certificates, self-signed is counter productive. There are certainly improvements to be made to the experience, but none of that can explain all these nuances in a way a temporary visitor will read and grasp. OTOH, it's easier to teach them "HTTP unsafe, don't type anything private".