In reply to:

set their TV to stretch the 4:3 picture to 16:9



A lot of people with w/s TV's are still using terrestrial signals and switching the 14:9 letterboxed picture to 16:9 mode - some TV's (like mine) don't have 14:9 zoomed mode so are pretty much useless without a decent source. There is/was a thing called "PALPlus" which made TV's switch to w/s automagically but I don't know if it's still used.

Gareth