>Why wouldn't we want to be able to [run interactive apps] web with our devices?
Because the web is for hypertext, which means static content. Images, text, video and audio clips, tables, code snippets, etc. Of course even that subset it does unimaginably bad, okay? Interactive web apps fucking suck, so that takes care of that 50%. For the other 50%, which is document viewing, why in the hell would I want pages to be able to move stuff around and create their own custom UIs and color schemes for every document I view? That use case is for magazines, a content-free medium. It's actually hilarious how people think hosting their library documentation on some stupid website like readthedocs.io, or publishing scientific journals behind IP blocklists (aka misconfigured bullshit from some charlatan sysadmin) is "progress".