This may not be what Pixar intended, but I see USD as a format for me to export from an editing application (when I’m done) and consume in an AR-based iOS application. If I want to buy and integrate an asset into something I’m working on, I prefer to use .blend files (although I’m willing to settle for FBX and OBJ).
USD is an interchange format and runtime. It's meant to preserve as much of the scene as possible as you go between different applications and allow for parallel editing.
Houdini is a great example of this.
But yes, you can also just use it as a last mile format. Though that's certainly not the main purpose
