"This makes so much sense to me. I've been a part of many "group" activities (mountain biking, skiing, etc.) where folks made no attempt to stay together. That has always baffled me."

I'm one of those folks who goes backpacking with some groups where we all often hike at our own pace during the day (so I end up, purposely, hiking alone for most of the day) and gather around the campfire (or just gather, if no campfire) for dinner and chatting and laughing at night (and sometimes at lunch). I really enjoy such trips - I get some solitude in the wilderness, which I enjoy tremendously, but still also get the camaraderie inherent in a good group at the end of the day, which I enjoy tremendously. Best of both worlds to me.

I should add that we're all experienced backpackers and trips are designed as described above.