The idea is that instead of adding a nonsense file, you use the native .gitignore functionality.

".gitkeep" is just a human thing; it would work the same if you called it ".blahblah".

So their pitch is that if you want to explicitly keep the existence of the directory as a committed part of the repo, you're better off using the actual .gitignore functionality to check in the .gitignore file but ignore anything else in the directory.

I don't find it amazingly compelling; .gitkeep isn't breaking anything.