It is a little surprising, and I agree, the docs here are not doing a particularly good job of explaining it. It might help to ask: if you don't explicitly commit, how does Kafka know when you've processed the messages it gave you? It doesn't! It assumes any message it hands you is instantaneously processed.
Auto-commit is a bit like handing someone an ice cream cone, then immediately walking away and assuming they ate it. Sometimes people drop their ice cream immediately after you hand it to them, and never get a bite.
Auto-commit is a bit like handing someone an ice cream cone, then immediately walking away and assuming they ate it. Sometimes people drop their ice cream immediately after you hand it to them, and never get a bite.