Despite the importance of individuals coming together for social group-activities (e.g. pick-up volleyball, chess clubs), the process by which such groups coalesce is poorly understood. Existing theories focus on adoption and contribution rates, group types, and the formation of group norms, as opposed to the processes involved in initial group coalescence. We address this gap in the literature through an interview study examining: 1) how well people's needs for social group activity engagement are being met; 2) the challenges they face in finding and participating in, and; 3) leading interest-based group activities. Our findings highlight how people's needs are not being addressed by current technologies. In particular, they place a heavy burden on individuals to step forward into leadership positions where the return they will receive for their efforts is often unknown, or extremely limited. We discuss the implications of our findings for the design of interest-based group coalescing technology.