This one needs a short history lesson…

In the early days of electronics, everything was powered by valves. There was no alternative. Then a new invention called the “transistor” took over. Transistors replaced valves quite quickly because they are smaller, lighter, cheaper, more efficient, and more reliable.

The invention of the transistor was the beginning of the revolution that made electronics more and more powerful and much smaller.

Early transistor gear had some problems though. They didn’t sound as easy on the ear as the existing valve gear. They got a bad reputation in some circles.

That problem was solved quickly, and modern gear sounds excellent as a result.

But a small group of people stuck with the idea that using valves for amplifying sound resulted in a more natural, pleasing sound that was less fatiguing to listen to.

And so, decades later, we still have amplifiers made with valves. And they sound better than ever, because we now use modern electronics around the valves to give them a cleaner signal and keep them at their optimum operating conditions, far more closely than was ever possible in the original valve era.

Plus they look cool. Much more attention is given to their aesthetics now than in the past.