Also, once HFS+ was released there was really no reason to stick with HFS. Arguably, HFS was defunct by a year or so after HFS+ came along.
There were basically no drawbacks to switching, and a significant benefit in terms of efficient disk use. The one question I would have, though, is that my memory is that for compatibility, an HFS+ volume is contained in an HFS volume. That would imply that some code must still be able to handle at least enough of HFS to enable HFS+.
Dave
Not to mention that it will make the efforts of those who take the time and effort to upload files to archive.org in vein if, eventually, a lot of that archived material can’t be accessed by a modern OS and/or modern hardware. Just because a format is older and fallen out of use doesn’t mean it’s worthless, either.
Thanks for your reply!
I generally agree that it’s not unreasonable for Apple to have dropped HFS support, but on the flip side, they still support FAT volumes – and that format was introduced a year earlier in 1984 and on a non-Apple platform.
Not quite. For external disks and disk images, HFS was still important for several years so that older Macs could access them. There were still many Macs in use that couldn’t run Mac OS 8.1.
If you mounted an HFS+ volume on an older Mac OS version without support, it appeared as an HFS volume with a single SimpleText file that provided information about HFS+ and how to access it. I don’t know how this was achieved – it could be that the initial information in HFS+ looks like a small HFS volume to an HFS OS, rather than the HFS+ volume being wrapped in an actual HFS volume.
FAT was actually introduced in 1977. The difference between FAT and HFS though, is that FAT is still actively used, in embedded systems, on things like digital cameras, on flash drives and media cards, and on the boot partition of PCs. It’s also the de facto standard for interchanging media between Windows, Linux, macOS, and miscellaneous devices, which is probably why Apple still supports it. None of that can be said about HFS, which was effectively obsolete in 1998.
8-bit FAT for 8-inch floppies was introduced in 1977, I wouldn’t bet that Big Sur could successfully read it even if there was some way to get an 8-bit FAT file system onto a Mac! I think what we refer to as FAT now is the 16-bit version introduced in 1984.
Agreed, removing FAT would cause problems for many people (especially as compared with removing HFS). It is amazing that it’s still in relatively wide use, but I guess it more or less works so people keep using it. But HFS was also used on embedded systems, what are those people supposed to do?? 
Definitely. Emulation is a good option, as long as your emulator can mount an image (probably as a CD-ROM) or access a physical optical drive.
I don’t know. There were plenty of announcements. HFS went read-only in Snow Leopard (10.6). Apple said they were dropping support in Sierra (10.12), even though they kept running with a warning to users.
So everybody using HFS should have known they were on borrowed time for quite a long time.
If someone has HFS hard drives (or floppies) and hasn’t converted them to HFS+ by now, I won’t be very sympathetic.
My big gripe is that there’s a lot of historic documentation on HFS formatted CD-ROMs, which are now pretty awkward to access. What we need now is some developer who is able and willing to write a friendly drag/drop wrapper around hfsutil so the rest of us can browse those discs and access the files in a convenient way.
Hmmmm… I wonder how open the file system driver API is on macOS. If there is a third party library for reading HFS, I wonder if that code could be made into a file system driver which could add support to modern versions of macOS.
Regarding: “My big gripe is that there’s a lot of historic documentation on HFS formatted CD-ROMs, which are now pretty awkward to access.”
This was my point exactly. Archive.org is full of files like this. The .iso image I provided the link to was a CD-ROM image itself. Conversion software or emulators (at the least), need to be readily available through time so that decades of computer information and history are not unreadable for future computer users. The “it’s an old and out of date format, so who cares?” attitude would not be tolerated in any other subject.