I'm not part of Apple. But I can say this, with
23,000 compatible products (at one level of compatibility or another), imagine the time it would take to make even half those products compatible with every single update that needs to be released? Backup your data, and don't assume that all the products you use have been tested. The developer of the software you use, not the operating system developer is responsible for making sure their software is to spec with the updates. Edit: and I've written a FAQ on why you should backup more frequently. It isn't just an issue of compatibility:
http://www.macmaps.com/backup.html
If you don't backup more frequently, hardware failure, accidental data movement, can all lead to issues where a backup is needed. Don't ever assume your data is safe in one place only. Make backups.