I'm not sure why you'd come to the conclusion that nobody uses on-site translation. Have you never visited a non-English site that you wanted to read/navigate but couldn't? Even if the translation isn't perfect, or even great, it's better than understanding 0 words and it's more than enough to navigate a page or to capture the essence of an article. It isn't a daily occurrence for me, but it happens often enough that I'm glad that this is happening. Switching to Chrome just for that was annoying.