Sure, but if someone wants to part extra money for the privilege and it's trivial to do, then why not? USB won't be around forever. Eventually everyone will have to understand a new interface. I certainly want a dedicated port for my line6 and the TB port sits there on my mac, unused.
TB3 does make it easier though since it shares USB protocols.
We'll probably end up getting another Helix at some point but it wont be used as an interface there unless it really makes a particular instrument shine that wouldn't in a dedicated piece. You never know, though. Certain things just sound good together.