The curing and working of wood over time as it is exposed to oxygen and repeated vibrations from playing is a real phenomena that results in a more immediate response and a drier, open sound. Beyond that, wood will take on emphasized frequencies based on what’s been played on it 
for many years.
But the virtue of buying older instruments doesn’t only relate to tonewoods. Hardware settles into place. Parts get used to the duty of holding a certain tension. Previous owners (if they receive what the instrument tells them) learn what string gauge and tuning really brings out the best in an instrument.

Even if you sell to or buy used gear from smaller brick-and-mortar 
shops, you’re helping musicians.

They are usually run by a handful of people who are musicians themselves, not MBAs. And the original person who brought the item in is still getting paid.