I wouldn't go quite as far as saying people "have to" use Facebook, but there are fairly significant social costs to someone who chooses not to.
Many people's friends communicate primarily via Facebook, and you can't just get around that by using phones and emails. People have discussions, invite people to events and post important life updates on Facebook. Often the primary communication mechanism for an organisation or even a local business will be Facebook. And they often won't re-circulate all that information via email just for the benefit of people who don't use it.
And yet people insist on trivialising these costs, and blaming individuals for this massive invasion of privacy because they chose not to incur these costs, rather than questioning the circumstances that have led to people feeling forced to make such a choice.
Do you really think the people who are having their privacy violated explicitly chose that trade off because they're "lazy"? Or do you think, presented with a choice between signing up to a seemingly innocuous helpful website, or encroaching social isolation as their friends start using it, they chose the former?