- Because it's not a hardware project at all then. Using transistors versus tubes is still a hardware project on the same level of abstraction.

- You've not gotten away from hardware; it's still there.

- You're using billions of transistors to simulate the operation of dozens of transistors/tubes, which is inelegant. The chip with those transistors may be small, much smaller than your project, but, in theory, your design with the few dozen transistors could be shrunken down to a chip that would be barely visible to the naked eye.

The guy knows that tubes are not the most efficient way to implement this. He's making it with tubes because it's cool. It's not that hard to understand.

The topic has changed in this subthread; this is now why build something (with discrete components, be they transistors or tubes) rather than simulate.

The educational value of building hardware is obvious to me; it cannot be replaced with simulation, and simulation runs on hardware that someone built, who knew how.

Good to know that the topic has changed. Let me know if it changes again!