Apache license doesn't forbid anyone to integrate your code and release the combination under proprietary licenses. The only requirements are to keep the licens

Apache license doesn't forbid anyone to integrate your code and release the combination under proprietary licenses. The only requirements are to keep the license file and the copyright notice intact, and to state changes if you choose to publish the modified source code. Therefore, it doesn't make a difference to have a CLA or not. What you trying to avoid is already allowed as per the license. However, some CLAs require you to declare the originality and ownership of your contributions. Maybe that's why they require a CLA to be signed for contributions.