It's possible that a new version could have a breaking policy change. For example, all our intranet apps are served over HTTP. At some point, that's going to become untenable due to the changes for browser security requirements.
In general, there's no momentum to make a change that the agency doesn't "have" to make, and when the browser finally refuses to transmit forms over HTTP then we want to know about it before the change is deployed to all the users.
In the days of IE it was common because certain tools would only support certain versions of IE. Intranets and specialized web portals (like ticket systems) for example.
