even the tube sockets are gold over solid copper ,most are cheap brass.Gold plated tube sockets are unreliable- gold is very soft as metals go; when tubes are inserted and then removed gold is scraped from the contacts of the socket. In time, the underlying metal is exposed; in this case copper. It will then blast the remaining gold off of the contact surface as it corrodes (which is does rather quickly). The result is a bad socket.
If you want reliable sockets go for a tin-plated socket. Tin, like gold, does not corrode quickly but its much harder and so the socket can last decades longer. There's no downside for sound quality either since tubes usually have tin-plated pins.