&gt;<i>If an OS upgrade breaks lots of programs or even one heavily used program, chances are users will blame Apple, not the developers of said apps.</i><p>The user just knows said program doesn&#x27;t work. And it&#x27;s not necessary that an OS upgrade will break lots of programs that a user has, it can break this or that program in subtle ways, or classes of programs (e.g. those using the X api) of which a typical user will have only few installed.<p>E.g. if it breaks third-party camera apps, users might not normally have 5 of those, to see that they all break at the same time, but just 1 additional on top of Apple&#x27;s (if that).