I work for a company that has a "managing" application that runs on windows. This application has a browser plugin that runs in an equivalent IE7 environment which must be supported.
Unfortunately that is what you get with proprietary sometimes.
I always hear about these applications but I've never actually seen one.
If he's a developer for a company that still has apps that require IE7, then he needs to support IE7. It doesn't need to be on the public Internet at all.