For example, imagine if your web application offered inline installation of a Chrome extension. If that installation should fail because of an issue with the Chrome Web Store or Chrome itself, you're likely still going to want to offer the user whatever explanation and advice you can. In doing so, as a nicety should you include an apology for the inconvenience the user is facing? Or is that confusing the issue?
Today's Internet software (as well as hardware) is so interdependent that there are a myriad of situations where such a situation can arise (and especially around the use of APIs).