You are being tracked, and your network is identifying you (tagging, mentioning you, posting photos that include you etc) whether or not you use Facebook.
This is like telling people who have privacy concerns about 23andMe / Ancestry DNA "just don't use them." Meanwhile their parents or siblings happily open up the floodgates.
The fb ecosystem is widely used, many times as a third-party library in many apps. Sometimes those apps send your data to facebook, sometimes they do it for free as a consecuence of integrating their services. And then, there are the "share with facebook" and "I like this" buttons.
They're called shadow profiles. If you do a search for facebook shadow profile you'll find a number of articles that talk about how Facebook infers connections between Facebook users and non-users.
Check out Facebook Analytics.
It's used in many smartphone apps, on websites etc. It is an analytics platform free of charge for the website/app operators (and gives FB a huge insight into non-FB users on the side)
This is like telling people who have privacy concerns about 23andMe / Ancestry DNA "just don't use them." Meanwhile their parents or siblings happily open up the floodgates.