There are many other uses for forums than simply socializing. The general AT forums (aside from the "Social" section which does include ATOT) are not the same as a Twitter, Facebook, Myspace, Instagram, Tumbler, Vine and whatever else the 'flavor of the month' social media site is.
Besides, who is to say that I don't think that the AT Social forums aren't annoying? P&N certainly is. ATOT can be at times. The Garage and Health and Fitness can have more useful purposes than to simply show off what you're eating for the day so I'm not sure that they are 100% 'Social'. I suspect that they are in the 'Social" section of AT because they do not fall under Hardware or Software of the technology world.
I assure you that I will never be able to get help from Facebook or Twitter on hardware and software issues that I could find on the AT forums.