There were commercial computers that did. The PDP-8, as one example (not 74xx, but similar).

Edit: The Xerox Alto CPU was built with 74181 chips.

Cost, power consumption, space, etc, are all disadvantages. I assume the Gigatron is using modern 74HCxx CMOS chips, which consume less power than the original 74xx TTL chips.

Yes HC didn't exist and 4000 CMOS was slow. Plus the pcb, assembly and test cost for 40 DIP packages is significant.

Typical discrete logics designs were much larger than the Gigatron. So they're not the same. Using 74LS the single board draws 2.5 W.

The short answer is that computers with CPUs made from 7400 series TTL existed, but they weren't "micro".

The Kenbak-1 might be considered an exception to the rule: http://www.kenbak-1.net/index.htm

The simplicity of Gigatron is compensated by the large memory that was extremely expensive.

This is a much more profound insight than is readily apparent. It is really easy to build a Turing machine -- except for the tape. You could probably build a universal TM is a lot less than 930 gates. All hardware design is essentially nothing more than taking common design patterns and moving off the tape and into the engine so that the tape can be more compact and the machine can run faster.

This is the main reason I personally find actual hardware re-implementations of old machines to be fairly uninteresting. There's really very little sport in it once you know the trick.

74 series gate golf to get the most compact hardware brainfuck implementation:

http://grapsus.net/74/

I have to admit that is pretty cool in a sick and twisted kind of way.

It doesn't need a large memory if remove the video, or if you change it to B/W.

930 logic gates + 1K of microcode ROM (so how many gate equivalent is 1K of ROM?) and it only runs 1/4 speed of a 6502.