You can, you use APIs.
I wrote a reply to you here: https://news.ycombinator.com/item?id=12655745
You can't do what I'm suggesting already. You're thinking of sending data to backend APIs which is completely different from sending data into a visualisation function.
It however does make it easier which increases the chances of useful innovation occurring naturally.
When software moved first from the shell to the desktop and then from the shell to the browser it became less accessible and less interoperable.Why shouldn't we be able to one day pipe Unix tools directly into our Web apps?