Same with languages. It's incredibly annoying when pages try to guess what language I want by my location, I rather be asked.
Same with marrying the language to the country, if I want to buy a flight from Germany, don't change the page to German!
Same with marrying the language to the country, if I want to buy a flight from Germany, don't change the page to German!
In other words this header is the most reliable piece of information to know what language the user wants. Somehow big tech decided IP geolocation is more reliable.
Do use the header, but always be open for the user changing the language too.