Browsers are not editors. I think it is that simple - mentally, the model is browsers are for consumption, so who cares about state? Contrast that with people

Browsers are not editors. I think it is that simple - mentally, the model is browsers are for consumption, so who cares about state? Contrast that with people writing editors - the mere idea of tossing the user's edits randomly is simply absurd. Add in creepy surveillance features like javascript to capture your pre-submit edits and the other awful crap people get up to, and I write things in editors and paste in to browsers.