1) what's so fascinating about retro tech? Is interest increasing?
History and memories of the old day I would guess. The interest is increasing as far as I can tell, but mostly on the 8 bit micro side. The plastic computers of the 80s. There is a pretty large game hoarding scene and those people are going after anything and everything. Perhaps a speculative bubble of some sorts similar to housing, 90s era pinball machines and beanie babies. There are a number of Nintendo carts that sell for more than they cost new, and some games in the original boxes sell for $300+. Anyone looking on craigslist for retro computing stuff I'm sure has come across the fishing posts looking for the goods.
2) is retro tech practical or nostalgic?
Nostalgic
3) does retro tech have any advantage over modern tech?
From an educational perspective easier to master the computers?
No different than classic cars.