It's not even just Facebook, every site does it', even reserving an item in Argos, you HAVE to provide your email, even though they also use your phone number to text the info, it's all going to be sold. The Irish government thinks it's such a great idea, they want to tax the money generated by the sale of your information. >.<
Why not use the email to send the information? Strange. Usually is a good idea to have a burner email account for that kind of stuff. But yeah the idea of Facebook and "if it's free, the product is you" isn't anything new. Always best to lie on social media
Somewhat related -
https://www.eff.org/deeplinks/2018/03/new-backdoor-around-fourth-amendment-cloud-act
https://www.eff.org/deeplinks/2018/02/cloud-act-dangerous-expansion-police-snooping-cross-border-data
Must be tough to keep morale up for EFF members