I never really got why facebook was considered interesting. I made an account because I was pressured by some female friends into doing so but I never log on it (at least 5 months). I know I'm not the norm but still, I feel like facebook is just a fad and that people will get bored of posting every second of their life onto the internet eventually.
The friction of sharing and reacting to life milestones with all your friends and family is an order of magnitude easier on Facebook. For example, try teaching a grandparent or technology inept uncle how to see photos of grandkids/nieces/nephews through email vs checking Facebook...
My kids grandparents are more appreciative of a photo in a frame or a drawing on the fridge than an image on a screen. Of course they can pick and choose if I chose to post those photos on Facebook, but I also take pleasure in curating and actually spending money to create a print (if I spend money on something, I'm more likely to do a good job.)
The definition of "keep in touch" varies for people. If you only use email, you are probably not sharing bulk pictures of family/friends events etc. Why would you use email for that ? I understand that you could get a picasa etc. link in emails but it is easier to use fb. Not to mention the funny comments on pictures.
