Comment by rconti

What does this have to do with System 7?

Operating systems have always used their own filesystems, and it persists to this day.

The only obvious exceptions that come to mind are iso9660 as a standard for CDs, and people generally go out of their way to use FAT/FAT32/whatever on USB keys and SD cards for compatibility with cameras or whatever device they're plugging the card into. But the latter is a choice users actively make to ensure the FS is compatible with the device, rather than a default.