Why do you think your email is private? Is your email provider more aligned with your interests or more secure than OpenAI? I doubt either Google or Microsoft care about your privacy (no difference).
And Google and Microsoft don't care about your privacy but they do care about being the only ones to profit off your data. OpenAI don't make profit off of your data, but they are collecting it; how they choose to make profit off of it in the future could be completely orthogonal to your interests.
Hell, China or any other of the numerous wealthy baddys could buy OpenAI and have access to all the data they're storing.
Amazing that you're so blase about this
Emails are "personally identifiable".
Your email can be used to link almost every online purchase you've ever made for example. That is what makes them dangerous, and it's what we need to change to improve privacy. It should be possible for companies to send invoices and shipping notices without linking the order to the customer's email address (or their name, or street address, or any other personally identifiable information).
We're a long way from being able to do that with invoices and shipping notifications but there's a lot of other systems where emails aren't necessary and shouldn't be associated with a record - even though emails are not private.