I think employers have figured out that accessing applicants’ and employees’ Facebook accounts is a back door to acquire information that is illegal to request on an application. You can’t ask a person’s age, gender, race, etc., on an official application, but most of that info is shared freely on social networks. Demanding access is stunningly illegal for this reason alone
(Most applications have a section asking for some of that info for diversity reporting, but filling it out is optional.
I suspect there’s a thriving underground market for information just like there is for body parts.