Documentation is very useful today (to clarify our thoughts on what is useful and what is not, what is in scope and what is not), and for our future selves.
Writing small bits of software made me appreciative of the work teams put on large pieces of infrastructure!
I am happier when I see copyleft but let’s be honest, I would contribute to an interesting, useful project regardless of their choice between MIT and GPL. Same for companies: some prefer MIT, but there is no way they are not going to contribute to the Linux Kernel just because of copyleft. So bottom line is: make something that people enjoy/find useful and see contributors flocking.
CLAs are a different matter: I do not contribute to projects which ask you to assign them copyright unless I 100% trust the organisation behind them.