I call nonsense on it - they’ve never heard of a post office or where one is?
I'll bet it would not take much effort to find 30-year olds who have never mailed anything. They've never been to the post office. They've never purchased a stamp.
If they get to the post office after the desk closes, they’re out of luck...no stamp machines in the lobby. I’ve directed people looking for stamps to the nearest grocery store on a few occasions.
You can even buy stamps at a lot of grocery stores now.