Best. Release. Ever.
Say you're tinkering with part of your program in the REPL, and want to try out a library you found online. Instead of losing whatever test data you've loaded/transformed, etc you can just call add-lib(s) and try out the new (potential) dependency. Equivalent in Ruby would be having a Rails console open and loading a new gem without editing Gemfile, running bundle and restarting the console.
Sounds like borkdude could like #3 more as that sounds useful for babashka.