Because there's no way to make that one connection that works well. IPv6 transitional state is fundamentally less stable than IPv4. If you mean that one connec

Because there's no way to make that one connection that works well. IPv6 transitional state is fundamentally less stable than IPv4. If you mean that one connection should be able to use multiple address families and addresses, then yes. It would be great, but at a much higher complexity than just making several connections at once and then discarding all but the first succcessful one.