I, too, made various friends at the school gates. Once we moved house, the friendships ended, and I made new friends. They fizzled out when the kids all grew up. I've made friends at each and every job I've ever had, too....and I've had quite a lot of jobs. Each friendship (if you can call them that) has resulted in perhaps one or two actual proper friends, but LOTS of acquaintances. For me, once the connection/common ground has ended, that's it. Like Facebook, most people are not real friends, but just people I've known along the way.
I've got 5 actual friends - they are people I know would help me out if ever I needed help (and I'd do the same for them, and have done so)