I learned to type in 6th grade at the age of 12. Granted, it was on an electric typewriter but even those made loud clacking noises and had a dinging bell when you got to the end of the margin. My mother had given me her old portable manual typewriter to practice on when I was at home. It was portable but still cumbersome and that thing was LOUD.
When I left high school I was typing 80 words per minute (I probably do 100 wpm on a computer). Typing at that speed on an old typewriter is loud (imagine the sound of 30 girls in a classroom all typing at once).
I also fail to see how using a vintage typewriter in a place people go to have a meal, a coffee, or conversation over a snack/drink adds ambiance to a café. My vote is for rude, pretentious, and attention seeking.