I am in strong agreement that there should be a character limit, and I'm even convinced that my 180 character wide terminal is longer than what would be an appropriate limit. But 80 characters is less than half of that, and so I'm not convinced that honoring a default 80 character limit is going to make anything more readable, more likely that it will just result in me turning up my font size so there is not so much unused space on my screen.
I think it's also true that most people use a larger than 80 character wide terminal today.
I guess the point is, without getting hung up on this knob in particular, that fewer knobs is pretty much always better; at least that was the central theme of the issue where I got the idea that Rufo maintainer team has this outlook: https://github.com/ruby-formatter/rufo/issues/2