Thanks to Cap'n Bry, here are two reasons given by him for why we couldn't send pong/queryhit directly.

quote:
Well, that would require you to create a connection out to the person who did the ping. You don't want to do that because:
-- There's overhead of creating the connection, sending the data and disconnecting. Not really that major, but there's alot less work if you just transmit rather than going through all that new connection rigormorah.
-- There's a chance that the originator is firewalled, meaning the only way to get a message back to him is through the network.