It very much has been exploited since the beginning of computing https://en.wikipedia.org/wiki/Tempest_(codename)
I'm pretty sure passwords are not shown to reduce shoulder surfing, especially from across the room.
If you want to steal a password, all the cool kids use a microphone or your phone's accelerometers.
https://arxiv.org/abs/1609.09359
https://www.cise.ufl.edu/~traynor/papers/marq-ccs11.pdf
https://phys.org/news/2017-04-criminals-pin-tracking-motion....
> A cathode-ray tube (CRT) is a vacuum tube containing one or more electron guns, which emit electron beams that are manipulated to display images on a phosphorescent screen.
https://en.wikipedia.org/wiki/Cathode-ray_tube
That causes a bit more signal than a keyboard, mic, or MEMS accelerometer, eh? :)