It has probably been said in this very thread before but here goes nothing. Here is why I made some of my own code open. Some of it was college stuff. I wrote assignment programs and made them open so others can see it. (I am almost the only one in entire class who can write code that does not suck) I made it open so others can understand.
One other project I made open was because it was a practice code and I wanted to show it off and maybe (again) help others who want to do something similar. I also made it open because I didn't intend to work on it anymore. One time job, so if someone else finds it of any use, they can commit to the main repo and improve the source repo instead of keeping the changes to themselves. And in the likely case that no one commits anything (no one has, yet) I wanted it to be somewhat of a demo code in case I wanted to show my skills to someone quick or impress someone.
One other project I made open was because it was a practice code and I wanted to show it off and maybe (again) help others who want to do something similar. I also made it open because I didn't intend to work on it anymore. One time job, so if someone else finds it of any use, they can commit to the main repo and improve the source repo instead of keeping the changes to themselves. And in the likely case that no one commits anything (no one has, yet) I wanted it to be somewhat of a demo code in case I wanted to show my skills to someone quick or impress someone.