It's not so much privacy for me as just apathy. Nothing about Facebook interests me.
Perhaps because you haven´t found any interesting groups to join.
I´m member on a couple of educative groups; one that gathers historical photos of my birth village and one war historical group.
Could be. I guess I dink around enough on the internet though, no point in seeking ways to waste more time!

Plus, Facebook's business model and actions are morally objectionable to me and I don't trust it with my data.