If we assume, as many do, that we are going to delegate the work of "understanding the code" to AI in the coming years, this surely becomes even more important.

AI writing code and commit messages becomes a loop divorced from human reasoning. Future AIs will need to read the commit history to understand the evolution of the code, and if they're reading poor summaries from other AIs it's just polluting the context window.

Commit messages are documentation for humans and machines.