Absolutely! They want to have standing in court so they can defend infringers, and that's materially easier to establish with copyright assignment agreements.
So while I agree with other commenters that a CLA is a clear indication that the entity seeking to have copyright assigned wants to reserve the right to take some kind of legal action at some point (like changing the license), it also applies in cases where the legal action is benevolent rather than malevolent (like defending the copyright).
