It also has an impact on contribution. In my experience with small open source projects, if I licence my library permissively, people will almost never contribute or open source anything. They will gladly ask for bugfixes and features, though.
If I use a copyleft licence (I like EUPL or MPLv2), it doesn't mean that they will open clean PRs, but at least they have to publish their changes in their own fork. It has happened to me that I could go read a fork, find a few things that were interesting and bring them back to my project.
With permissive licences, the risk is that those (typically businesses) who keep their fork open source probably don't see a lot of value in their fork, otherwise they would have made it private, "just in case".
If I use a copyleft licence (I like EUPL or MPLv2), it doesn't mean that they will open clean PRs, but at least they have to publish their changes in their own fork. It has happened to me that I could go read a fork, find a few things that were interesting and bring them back to my project.
With permissive licences, the risk is that those (typically businesses) who keep their fork open source probably don't see a lot of value in their fork, otherwise they would have made it private, "just in case".