> Because before js became popular, every web app had access to every single event execpt what, scroll and mouse position.

Huh? No, they had access to basically nothing unless the user did something that triggered a network request. What did you type in that form, but delete before submitting? No visibility. Which parts of the page did you linger on the longest? Which parts of the text did you highlight? No visibility.

They could see when you requested/submitted stuff, but that was about it. Pages couldn't sit there looking over your shoulder while you were using the page.