Comment by Arnt

Software is a collective. A billion or so people get the same software. The time for self-signed certs has passed because supporting that in software for a billion people opens up some of that billion to attack.

The few people who understand the niceties of certs can create a private CA, trust that, and use that CA to sign a regular cert. Doing that is nontrivial, but it doesn't put other people at risk.