This is a great question. Many people think the AGPL solves this problem but it absolutely does not. This is why MongoDB, which was AGPL licensed, just changed to a custom license.
The other reason we don't want to use AGPL is that it can be quite aggressive in making you open source your own code if you want to embed our code in a proprietary application. We actually think building proprietary applications is a fine use of our software, and is one of the major use cases for this kind of infrastructure. This is addressed in more depth along with many other questions in this FAQ:
https://www.confluent.io/confluent-community-license-faq
The other reason we don't want to use AGPL is that it can be quite aggressive in making you open source your own code if you want to embed our code in a proprietary application. We actually think building proprietary applications is a fine use of our software, and is one of the major use cases for this kind of infrastructure. This is addressed in more depth along with many other questions in this FAQ: https://www.confluent.io/confluent-community-license-faq