why?

Why not?

GitHub is a website for developers and programmers to collaboratively work on code. The primary benefit of GitHub is its version control system, which allows for seamless collaboration without compromising the integrity¹ of the original project. The projects on GitHub are examples of open-source software.

¹ Some l33t hackers can manipulate integrity on Github.

Check out Contributors on SigMal
- One of them seems like they don't quite fit

Benefits

Github as a 'Code Portfolio'
- Show off your technical and coding expertise
Build Software Engineering Products
- Lots of production Code is on Github (i.e. Linux Kernel, cpython, snort3, etc)
For those BEAUTY GREEN SQUARES that make contribution

Just note there is always another person, with more commits than you!

Also use it as a place for information