So this hypothetical user is setting a different language and then complaining that they're getting that language?

It's not that complex. Say your OS or system setting is US English and you're downloading say, an app in Spanish that was developed with that in mind, you'd want that, wouldn't you?

It's not that complex. If I don't speak Spanish, I don't want it, no. If I do, then I'll go to my browser settings, and set my preferred language to Spanish.

But that'll translate the entire browser to Spanish, which you may* not want. All due respect, but you don't seem to be in touch with reality on this one.

Just because you speak a language, doesn't necessarily mean it's your preference all over the place. Or let's say you're Dutch and you live in the US. Your OS is in English, and imagine if telegraaf.nl auto-switched to English.

  (**) The web and apps are full of less than ideal translations. And AI has actually worsened it.

Well, I'm Greek and live in Greece, and el-GR/en-US has served me fine for decades.