Anonymous B joined in and replied with this 11 years ago, 3 minutes later[^][v]#558,584
Sometimes wires become loose or disconnected, and hitting them may cause contact once again.
Anonymous C joined in and replied with this 11 years ago, 4 hours later, 4 hours after the original post[^][v]#558,625
I thought it was something to do with jolting valves or big capacitors in old TVs, amplifiers and such.
As these appliances started being made differently, we retained this peculiar behaviour.
It is similar to how an englishman does not drink from the taps in the upper floors (if you know what I mean).
Anonymous D joined in and replied with this 11 years ago, 10 minutes later, 4 hours after the original post[^][v]#558,627