Mini-08 single-board computer based on the 8008 CPU [video]
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It probably comes down to nostalgia and "just to see if I can actually do it" in many cases
Electronically speaking, I'd note that the 8008 is early PMOS. Making it run is harder than your average 5 volt microcontroller (whether from the 1980s or today). Multi-phase clock, multiplexed address, data, and control bus, and a negative 9 volt power supply.
Regard it as an electronics equivalent of oldtimer cars. Some collect them, some want to preserve pieces of history, there's nostalgia, some like messing with 'antique' technology, some spend ungodly # of hours restoring them. And of course (if in working order) take 'm out for a drive on a sunny day.
Does it need explaining why some people do that?
Bringing old computers back to life, is more accessible than oldtimer cars. Cheaper, doesn't take as much space, no gasoline fumes, and portable so easy to bring to a meeting/event & show there.