Speed
The terminal is fast. Not just in execution, but in intention to action. A GUI requires you to find a menu, click through options, and confirm dialogs. The terminal lets you express complex operations in a single line.
Composability
Pipes are the greatest invention in computing history. Taking the output of one program and feeding it as input to another creates infinite possibilities from simple building blocks.
Reproducibility
A shell script is documentation and automation in one. When you do something in a GUI, it is lost. When you do it in the terminal, you can save it, version it, and share it.
Remote Work
SSH into a server and you have your full development environment. No VNC, no remote desktop, no latency. Just text over a secure connection.
The Terminal is Honest
There are no loading spinners hiding what is happening. No progress bars that lie about completion time. The terminal shows you exactly what is going on, character by character. In a world of abstraction, that honesty is refreshing.