Because application errors are not one-size-fits-all. Sometimes it's because of some specific flow being broken. Sometimes it's "the site is down". Sometimes it's a "there's an error condition that needs to be bubbled up to the user". And sometimes it's a poor internet connection being mishandled.

While code fixes are not in their power to do, changing their behavior, or waiting for a better internet connection (i.e. "something went wrong" actually means "go log in to the hotel wifi") are things in their power.