Gmail is reading your emails and attachments to train its AI, unless you turn it off
(www.malwarebytes.com)
When did they ever say they weren't scanning emails for ad words? Pretty sure that was in the April 1st, 2004 announcement. I found this article from then that says:
To finance the service, Google will display advertising links tied to the topics discussed within the e-mails. For instance, an e-mail inquiring about an upcoming concert might include an ad from a ticket agency.