I, too, remember the trifecta of APPEND, JOIN, and SUBST. And while I always thought they were interesting, I was also wondering for most of them when I would ever use that. At the time, DOS versions and hence applications for it that don’t know subdirectories didn’t cross my mind, as my first DOS version was 2.11, I think.
When I got my fancy 1.6 GB harddisk I used `subst R: .\cd` to run my games needing the CD in the drive from a directory on the harddrive instead. Boy did load times improve a ton.
SUBST was commonly used for source code directories. It served at least two purposes: making source appear at the same location on all machines and working around path length limits.
I've also used SUBST when reorganizing network drive mappings.
I, too, remember the trifecta of APPEND, JOIN, and SUBST. And while I always thought they were interesting, I was also wondering for most of them when I would ever use that. At the time, DOS versions and hence applications for it that don’t know subdirectories didn’t cross my mind, as my first DOS version was 2.11, I think.