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.

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.

Funnily enough at least in my personal anecdotic case it works about like that. I do just remember when my meetings will be (or look up where the meeting was decided on), do try to remember what I had planned (sometimes I forget, but almost always for the better), and written notes are rare enough that pen and paper are sufficient. And also don't have a driver license. I don't think my case is exactly rare, even among softdev croud.

The point, as I noted below, is that this is an impractical solution.

You can justify the value of any ridiculous invention by comparing it to a world-changing invention.

You have soundly defeated that strawman, well done.