Nice. It's free in the sense that for your Apple-apps on Apple-platforms you no longer need a commercial icon set with a license etc. On top of that, it's known

Nice. It's free in the sense that for your Apple-apps on Apple-platforms you no longer need a commercial icon set with a license etc. On top of that, it's known to work well, integrates with the UX, and because there is a good chance other applications in the same ecosystem use similar icons it'll be easier for the users to recognise them.