Unfortunately, the web today has strayed far from its original vision. Yet, we continue to rely on the foundational technologies that were created for that very vision.
If browsers catered to their user's desires more than they cater to developers, the web wouldn't be so shitty.
The primary benefit of web applications is they don't lose your data. Not a single web application UI that exists provides as good a user experience as the native desktop applications that came before. A web where browsers provided their own UIs for various document types, and those document types could not modify their UIs in any way, period, would be a better web. You serve up the document, I get to control how it looks and behaves.
Browsing without reader view enabled by default is like driving your car around with the hand brake engaged.