Why do you think it is "harmful to their search/ad business"?

I see as enhancement. It will not be long before Word and Google Docs is using AI to help people write copy, correct, and translate documents. Those are just the ones I can think of and I'm not that smart. Do you really think either Google or M$ will allow a 3rd party to control something that is integrated into their products? Only companies that are out of business do things like that.