I did the 6502 project in which you assemble a computer system on bread boards (wiring together the clock, cpu, ram, etc).
It helped solidify many of the concepts from nand2tetris. For some reason doing it all physically with real chips and wires made it all a bit more memorable.
I’d love to try his other bread board project in which you assemble all the inner workings of a cpu on bread boards as well — I think this is what you were referring to.
Hang on a second, does nand2tetris not involve real chips and wires?
This is largely about accessibility. If it’s tied to hardware, fewer people can do it. Additionally, real hardware means there’s additional opportunity for error due to faults in the hardware or environmental variables.
That said, Nand2Tetris could, in theory, be done with a bunch of 74xx NAND chips on a breadboard.
I know of a few people who managed to get a working Nand2Tetris computer on breadboards, but it took a lot more time and money than they thought it would.
On FPGA, though, it works nicely.