There are some pianos in airports, train stations, etc that are
there
for the public to use. Cheap entertainment.

And a nice touch, IMO.

Depends how good the members of the public trying it out are.

It matters not how profficient they are at playing.

A piano played badly is not a nice thing to hear.

Then don't stop to listen to it.

You'd hear it all the way along the corridor.

What a terrible experience for you.

Try to listen to this the whole way through, with the volume as high as
a real piano would be. https://youtu.be/YgKy5E9i_RU

I can imagine you walking past the piano being played badly and spotting
an upside down envelope and it stresses you out so much you have a heart
attack.