That’s Expression Engine driven. I would bet if I updated the underlying software, the newer versions would come with other options, but I don’t like to do that very often. (It costs money and it’s inevitable that the site will be down for some period during the switchover.)
If people really would like to use the networking features, let me know.
I don’t even use the stuff that’s there, much less Twitter, Facebook, etc., so I’m satisfied with things as they are.
I would think that anybody who wants to make their Twitter or Facebook contact info available to everyone here could put it in the the Bio section of their profile.