There is a meaningful difference between allowing someone to use your code for whatever and assigning the rights to it so that you can no longer use it. And re

There is a meaningful difference between allowing someone to use your code for whatever and assigning the rights to it so that you can no longer use it. And requiring contributions under BSD/MIT doesn't seem to be a huge problem for the projects that actually use those licenses. The bigger problem they have is that nobody uses e.g. FreeBSD because if they do anything interesting the code just ends up in Linux/macOS/Windows whereas the reverse doesn't happen.