"Searches without basic "signals" from a client are usually completely useless."
Maybe to you, but don't assume they are to everyone. I prefer unadulterated search results.
"If I happen to have my laptop in France, for instance, and my browser sends nil signals about my system (or the search engine doesn't query for them [duckduckgo]) then I will get google all in French, which I don't speak. Instead, my browser knows my preference for UK English, and google will see that and show me instead the contents of google.fr in English. "
Funny, but other sites are able to provide me with a method to select what language I see the text in. It is not necessary for a site to "guess" what language you want to see the text in. Supposing there's a need for me to see Google in French, while in France? If they force feed me content based on the engine's assumptions, rather than interactive choice, how does that help me?
"Similarly, I would expect to see different results if I searched for "window system" from a Linux box rather than a mobile or a windos machine. "
On the other hand, I do *not* prefer the search engine to assume what I'm looking for based on what OS I use to search. What if I *want* to see results pertinent to Windows OS or even windows for my house? Supposing I'm searching out technical problems I'm having on my Windows box from a second box running Linux? I would find it very annoying if I wasn't seeing results for the Windows OS in that case.
As a rational, thinking person I prefer the search engine to return results based on my search terms. I don't want it making assumptions which may or may not be relevant to me.