There is already plenty of commercial software that depends on other commercial middleware that needs to be licensed separately. Of course licensing each and every library is typically bit different in scale, but conceptually it is pretty much the same thing.

Sure, no one's ever bought Tableau along with a Windows Server license to solve their data warehouse analytics needs.

You're not describing a strict dependency. You can just buy Tableau and use it.

Presumably that's where having a single place to handle payments comes in handy.

It's (hopefully?) less "well, you have to go to this other person and license their software too" as much as "here's the total cost for a license (which happens to include both A and B)"