Today is the 30th birthday for Macintosh Programmer's Workshop. This is a re-implementation of the MPW Shell. Why? Well, a few years ago, I wrote an emulator/compatibility layer[1] to run MPW Tools on OS X. That works great except for Make. Since MPW was single threaded, Make generated a shell script instead of running subcommands directly. So to effectively use MPW Make, you need a full shell. And from there, being interactive isn't too much more work.
1. https://github.com/ksherlock/mpw