I'm a copyleft fan in theory, but...

In practice my experience is that anything GPL actually doesn't benefit the fellow worker/programmer as much. Since the worker probably works for an evil soulless company, he would have to use a different permissive software or buy something proprietary. I.e. if you choose copyleft you provide to a commons that is only accessible to a minority of workers. I also believe that most companies (even big tech) will try to contribute important or significant changes to permissive upstream projects instead of running their own private forks (the latter is much more annoying and expensive).