Companies like Facebook aren’t building technology for you, they’re building technology for your data. They collect everything they can from FB, Instagram, and WhatsApp in order to sell visibility into people and their lives.
This isn’t exactly a secret, but the full picture is hazy to most – dimly concealed within complex, opaquely-rendered systems and fine print designed to be scrolled past. The way most of the internet works today would be considered intolerable if translated into comprehensible real world analogs, but it endures because it is invisible.