Sounds like you haven't been working long enough to forget your decisions, which you WILL do eventually. In such cases, where you're looking at code you wrote 10 years ago and you find a weird line, when you view the git blame and read the commit message, you'll be very thankful that you explain not just "what" you did, but "why" you did this, something an AI will have a very hard time doing.

You don't have to if you don't want to, but if you think "this commit message is just a summary of the changes made", you'll never write a useful commit message.