It's very simple, the reason people favor a more permissive license is generally the same reason they open source their code: You want other people to use your project.

Obviously, a more permissive license is going to let people do whatever they want with "your" code, as it doesn't really belong to you anymore. If you want tight control then it's a bad choice, but a more permissive license is almost always going to mean your project is more widely used, for better or worse.