Interesting - I guess the amount of time spent and the degree of common goals, amount of common successes/failures do have a bearing on the strength of sense of belonging to a group. Maybe the experience you were getting in the meetups etc, wasn't scoring high on those points. E.g. you may be only spending 2 hours on the weekly football you play with your friends, but the sheer intensity of the shared experience in such a short time might give you more satisfaction than other activities you may be doing more frequently.