That gives you more rights than it gives me. I was always free to release my patch under the AGPL, why would I need you to do it? (well, if you do it I wouldn't have to maintain a fork, which is something I will admit).

It would allow you to maintain a proprietary product with proprietary features that you don't release under the AGPL and use my code within that product.

I like reciprical licenses, if I get code from you under the MIT license, I will give you code back under the MIT license (which you can use however you want to, under that license, just like I can.) On the other hand if you give me your code under the AGPLv3, I give you back code under the AGPLv3 (and you can take it or leave it, so long as if you take it, it is under the terms of the AGPLv3 license).

At least, that is my idealist stance. But in reality, practicality sometimes takes precedence, so I might make a minor bugfix or something. But then I have all the trouble of reading the CLA, making sure I understand it, and agreeing to it, so practicality may just as likely lead me to just file an issue instead and patch my own copy.