Gmail can read your emails and attachments to train its AI, unless you opt out
(www.malwarebytes.com)
Companies that build large LLMs have already said that this is becoming a problem. They're running out of high-quality human-written content to train their models.
Google paid Reddit to get access to their data to train their models, which is probably why their AI can be a bit dumb at times (and of course, the users that actually contributed the content don't get any of that money)