The results you get are very much dependant on where you are visiting from. I can set my everything to Japanese, both in my browser, OS and my Google user account and search via google.co.jp - but if I am not in Japan, results will be skewed away from Japanese websites.
For example: The other day I wanted to find the lyrics for the Japanese version of a song, so I typed "[song name] 歌詞" and because Google knows that 歌詞 means lyrics, and it can see I'm in Europe, my top result was an English lyric site, with the original version of the lyrics and no mention of the Japanese word from my search term. Technically, that is really impressive, but kinda useless.
On top of that, it can sometimes be impossible to visit help or product pages if you happen to be in the wrong country.