I haven't actually deleted my Facebook account, but haven't used it in years.

I never made a conscious decision to stop using it. I got really annoyed by Facebook emails and phone notifications, so I created a filter for Facebook email, and turned off notifications. Once it stopped constantly bugging me to look at it, I kind of just lost interest. At some point, I just realized I hadn't logged in in a long time, and noticed that I didn't miss it at all.