The best argument in favor of the command line is what we’re doing right here. People interact with each other with words. It’s a command line straight to the other person’s mind. It takes years to learn, it’s dense, but it’s code. Billions of ideas that can be expressed with symbols and syntax. Whether that code is English, German, Arabic, or ASL, the learning curve is worth the payout.
Programming a computer with code is simply the most powerful way to go about it. Whether that code is Bash or Powershell, BASIC or Ruby, the learning curve is worth the payout.