What is the use of doing all of these courses

Answer 1

To get xp and higher levels :) .... no but seriously it's to learn or refresh fundamental programming concepts across different languages.

Answer 2

If somebody wants to learn programming, somebody can start here.

Answer 3

you will not waste your time on other things and you are increasing your programming skill by simply sitting and you are able to know the basic of all courses that helps in you in your upcoming future.