With one-liners, you can:
- Edit previous command and re-execute quickly (Up arrow, edit, enter instead of Alt-Tab to Notepad2, edit, F2 or whatever, Ctrl-L). Okay, that's not much keystroke saving, but there's less windows/view switching.
- Utilize shell's tab completion to complete filenames, etc.
- Utilize shell's other features like brace expansion, environment variable expansion, etc.
- Pipe the output of script to other command; or receive other command's output as script's input.
- Easily redirect output of script to file.
- Store the previous commands in the shell history file.
Among others :-)