Billions of people don't use calendar apps so they're useless; just remember your meetings.

Billions of people don't use todo list apps so they're useless; just remember what to do.

Billions of people don't use post-its apps so they're useless; just remember what you're going to write down.

Billions of people don't have cars; just walk.

You can dismiss any invention since industrial revolution with this logic.

And I am pretty sure every single one of those "billions of people" have had the experience of returning back from the grocery store, only to realize they were actually out of eggs.