[Filligree]

> Aren't most browsers auto-configured to request the language they were configured in?

This may be true now. It was less true in 90s, where this logic originated.

[troad]

I don't recall browsers behaving all that differently in the 1990s. Per W3, re MSIE 4.0, in 1997:

> The Accept-Language header defaults to the current System User Locale ID but can be overridden by user.