We have differing views of "everywhere, today": you acknowledged yourself there are cases where it won't happen, it's just how much we think that's important where we differ. That's ok, I appreciate your point and thanks for spending the time to explain.
As for what browsers can or cannot do, they also can't introduce DNS-over-http, introduce stricter cookie policies breaking a bunch of web sites, or reduce effectiveness of ad-blockers, drop flash, or... Sure, defaulting to https is too high a bar (not expressing an opinion on any of those — eg. good riddance to Flash :) — but browsers can and have done stuff that's just as bad, forcing web site creators to adapt their web sites).
But to each their own.