Maybe you're not in control of the back end.
For example, say you were writing an app that displayed RSS feeds from different sources. You don't know what might be coming over the wire, so it would be useful to sanitize it at the point of display.
For example, say you were writing an app that displayed RSS feeds from different sources. You don't know what might be coming over the wire, so it would be useful to sanitize it at the point of display.