Remember that most European keyboards don't have [ and ] accessible on the first/second level. That's already half of the western civilization, not some random's custom layout.
I accept that U.S. English is the computer lingua franca.
Keyboard is a one-time investment of 20-200 Euro, but learning to use your editor efficiently is an investment of years of your life... amplified by the fact that there aren't that many good editors. So, any person who needs to work with the editor on a daily basis will have to make a choice between buying a keyboard that works well with that editor or a keyboard that allows them to type Euro / Pound sign more easily... And nobody in this situation is going to choose the keyboard that doesn't work well with the editor.
This obviously varies by country, but at the places I’ve worked at, most people used the local layout instead of the US one. They couldn’t bother relearning it and then switching every time they wanted to enter some text in the local (Slavic) language.
Has the US keys on the first/second levels and most/all special symbols for European languages easily accessible w/ modifier keys. Entirely removed the need to switch keyboard layouts for me.
However, even if I wouldn't switch - wouldn't it just be to remap the keys in my config?