The original problem was for load balancing, where the protocol is often not known, and backends might be reached over a WAN. There are some neat advantages possible from this method, such as the target application not being woken up early from accept() (etc) by preconnection, and the initiator being able to detect the health of a backend before choosing it as the target of a forwarded connection, but mostly I just thought it was an interesting abuse of an obscure kernel feature.