I think very few people will realize the systemic effects that a demo like this entails. Very, very good work StackBlitz team!
EDIT: Upon closer inspection, it looks like this is an online IDE meant to mimic a desktop environment. I don't know if there's any demand for that, but sure, why not. I'm sure someone will come up w/ a reason to run WebAssembly in a jQuery plugin, too.
Or a desktop-only Electron App would be usable from a mobile phone browser etc.