Because you want to be able do report your taxes documents to the tax office? It's one of those things that sound so simple on paper, but every time someone doe

Because you want to be able do report your taxes documents to the tax office? It's one of those things that sound so simple on paper, but every time someone does that trivial thing and not make documents available to the web browser, usability suffers. The real answer why the browser can read certain files is much more complex, your web browser is not a singular entity anymore. And the network and protcol speaking parts of it can't access your documents, according to the principle of least authority. It's far from perfect and gets hacked every time, but do take the time to read how that's done. The hacks are just as complex as the web browser itself. The practical problem with the browser is the enormous complexity of functions, everything from OpenGL to databases to p2p and usb, that keeps growing boundlessly.