Right now we have a client that needs an integration, but the company that wrote the software to be integrated will not provide documentation for integration unless we purchase their (otherwise useless to us) software. That is, software that would be tested at the client's location, with their data. In short, it is absolutely not something we need to purchase (or, honestly, even can -- we're a very small company).

So we eventually tracked down someone who had it, and we integrated as best we can.

Basically they were just putting up a wall to people creating integrations, which is the entire method by which their software is used. So... if you can't contract someone to integrate, why would anyone choose that product going forward?

And yet they do.