Like I said, tradeoffs. LLVM for example doesn't require copyright assignment, but does require a contributor agreement for patent purposes for significant contributions.

Contributor agreements are a necessary mechanism to protect the project and ensure its future when dealing with patents or preparing for the potential of relicensing.

Did you miss the part where I mentioned patent agreements which is another good reason why Contributor Agreements are important?

And while the Apache Foundation already has a "permissive license" it's not quite as permissive as BSD / etc.

And if the Apache Foundation wants to relicense, to say, a future version of their license, they're still going to potentially need that contributor agreement.

Again, as I said before, there are tradeoffs.