Originally Posted By: artie505
Under any circumstances, though, we haven't been prohibited from borrowing someone else's disc drive...yet. tongue

Yes but then there are issues of application compatibility, both my tax and accounting apps are old 32 bit. Actually all of that could probably be solved, but my point is historical/archival data backups we thought we could rely on, may/are not be as reliable as we thought. (1️⃣)

Originally Posted By: artie505
Can you think of a reason for the prohibition? Drive sharing seems pretty innocuous.

OFF THE TOP OF MY HEAD: AND in rough order of probability...
  1. The re-shuffling of functionalities between the system volume and data volume in Catalina made sharing optical drives significantly more complex and expensive to code and maintain (2️⃣).
  2. Because of the preceding not all features were ready for prime time when Catalina was released so rather than having a problematic minor feature it was simply dropped — possibly to reappear in the future.
  3. There was insufficient demand to make the cost of maintaining the ability worthwhile.
  4. It created a security vulnerability either on the system sharing the drive or the system "borrowing" the drive.
  5. Some or all of the above
  6. None of the above.

FOOTNOTES:
1️⃣ I am now creating all my new text files in markdown on the theory that it is easy to output in a wide variety of formats or in apps and is simple enough to remain compatible in the future.

2️⃣ There are multiple third party developers dealing with as yet unresolved kernel extension (a.k.a. .kext or driver) issues in Catalina or anticipated in MacOS 10.16 because "Apple has yet to fully document new APIs associated with drive access and I/O" which would seem to indicate the work is still incomplete.

If we knew what it was we were doing, it wouldn't be called research, would it?

— Albert Einstein