Might be one of the most absurd things said on here. Requiring a phone number for sign up does not automatically mean you are selling ads.
How do we get from there to "just assume every company in the world will sell your data in wildly and obviously illegal ways", I don't know.
The most simple version would be an ad-supported ChatGPT experience. Anyone thinking that an internet consumer company with 100m weekly active users (I‘m citing from their job ad) is not going to sell ads is lacking imagination.