WebUSB is a way to make it useful from day one => if WebUSB was marketed with this business goal, then why not (except nobody would buy it)? but the implications are so much wider, in terms of security and usability...

Why not WebSATA? WebPCI?

There are certainly a few key actors who would benefit from such a standard (benefits could be time to market), I'm just not sure it's enough benefits for the end user to justify a new standard!