Advertisement platforms extend beyond single platforms. Google Ads are on every website in the Internet, and Facebook ads are on other sites too. So even if you don't have a Facebook account and never visit Facebook itself, you will see their ads and they will start following you around and start collecting data on you.
I can just picture some girl I know saying, 'that Zuckerberg is a real creep. OMG. He literally follows me everywhere.'
even if they're not loyal to the platform, by showing the consumers ads it'll still make an impression for later