I like doing the organized events for a number of reasons, and I'm really anti-social.
I like that they provide the map/cue sheet, road markings, support, and food at the rest stops. I like doing their routes, as my own routes tend to get boring, even if they are quieter or more challenging. Or the organized event will be someplace I've never ridden, or seldom ride, so it's really nice to see new countryside, knowing that I will be riding a prescribed distance. On my own, in new territory, I will likely have no idea how far or how long any route would take.
I like that they often have photographers there, and they put photos up on their web site that I can download and put into my collection.
And being anti-social, I can choose to interact or not with the other riders, so the group aspect is really secondary.
Luis