Why doesn’t Google Chrome use the Google Search Engine spellchecker?
My answer to Why doesn’t Google Chrome use the Google Search Engine spellchecker? on Quora
Because the Google search spellchecker runs in their data centers, while the Chrome spellchecker runs on your local machine. Sending everything you type in to your browser to Google’s servers just to check spelling would be an unnecessary privacy violation, especially since local spell checking does a good-enough job.