There are many advantages!
1. you can see data or information visually
2. for most cases, it is easier to have the information visually displayed than with flashing LED lights or sound
3. with a screen, developers are able to build intuitive user interfaces and it is easier for us to use out computer with a display
4. when a developer has to code an application or something, it is better if the developer visually sees his code than hearing the the dedicated sounds of the keys or something
I can go on and on but I guess this is enough for now