You think regular end users having to set up and maintain server software in order to force a name for an IP is going to become a widespread pattern? That's horrifying. I don't want to live in that world.
To put this another way: it's a significant benefit for my random non-techie friends to be able to use this new feature plus HTTPSEverywhere. And even as a techie, I don't use a hosts file to block anything. So I'm not bothered by how Firefox chose to implement this, like most people.
That kind of thinking, really irks me.
It does bother me when Firefox introduces a feature which covers up a huge hole in TLS, and they get a large number of complaints on HN.
Mainstream users do not need most software ever made.