We sometimes put confidential information into task descriptions and elsewhere. Sending that off to an AI company is potentially bad. Doing it without an assurance that our data will not be added to their database for building responses is much worse.
I have turned the option off for my organization. It is great that you provide that option, but it should be off by default. Once it is a standard feature instead of a newly introduced feature (with email warnings), you will be potentially leaking confidential information for new customers unless there are big warnings at account creation and a few reminders after.