[latchkey]

If I have a file on machineA with uid10001 and I copy the file to machineB, I might want it to retain that uid, but it shouldn't matter to machineB that it doesn't map to a real user.

[rafram]

Hopefully that user actually doesn’t exist on the second machine!

[MrDarcy]

You’ll see this observation all the time building containers.

[danielrico]

Don't if you only run them with root user.

[kurisufag]

or with ipa-esque authentication schemes and shared mounts

[dimatura]

And NFS!