Sure if seems sketch to access USB from the web, but as a user if I'm trying to achieve something and I can't do it on the web, I'll end up installing a native app which has way more access to my system.
As a developer I would much rather be able to just deploy cool things on the web instead of having to package up native apps for every platform just to do things like read/write NFC tags, or send notifications to users who want them.