I couldn't speak to Outlook, but Outlook is both popular enough and has enough people locked-in to its ecosystem (as business users) that it doesn't have to worry about losing users if Accept-Language doesn't do the right thing. Companies have IT departments to fix that stuff.
I'm talking more like https://www.buerklin.com/. If that site comes up in the wrong language and the only way to fix it is to change the user agent's Accept-Language header, the user isn't going to just figure it out; they're going to navigate elsewhere. So the site has a bug in the top-left to toggle English or German.
Something you mentioned up-thread that I should have commented on but overlooked:
> which I find super odd; as if people are walking around using a browser in a language they don't speak
... yes, all the time. In libraries and Internet cafes, schools, and other shared spaces.
But then, that's not worse, because geoip would already be forcing those users into a language they potentially don't speak by not listening to their device.
Or your library has somehow misconfigured their PCs when setting them up?
A cookie based override already exists, forcing geoip is strictly worse as a default, except for localising currency? I guess.
I'm talking more like https://www.buerklin.com/. If that site comes up in the wrong language and the only way to fix it is to change the user agent's Accept-Language header, the user isn't going to just figure it out; they're going to navigate elsewhere. So the site has a bug in the top-left to toggle English or German.
Something you mentioned up-thread that I should have commented on but overlooked:
> which I find super odd; as if people are walking around using a browser in a language they don't speak
... yes, all the time. In libraries and Internet cafes, schools, and other shared spaces.