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.
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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.