They aren't doing this to improve the user experience with the software. They're doing it to address the perception that "new and shiny" is what people want -- not functionality per se. They're aiming at the user experience of getting something new.
You know that marketing slogan, "sell by showing what problem you solve"? The "problem" that marketers have identified is the public's disinterest in things not new and not shiny -- and lately, not thin.
In my view, incompatibility is a sign of poor vision, poor support, and a lack of respect for those people who have come to you for what you offer. Speaking as a developer, if I come up with new functionality that is incompatible with the old, I add the new functionality without breaking the old. There are almost always many ways that can be done. I never did find a worthy excuse not to do it, either.
It isn't Google, or Apple, or whatever vendor that needs to learn a lesson. It's the public. I don't think it can be taught to them, either.
Squirrel!