I totally get it with cabs, older ones are huge, cumbersome and very heavy, so I don't feel there's enough of a positive trade off for that, especially since most modern cabs just flat out sound better and can go louder and lower.
When it comes to amp heads though, age/weight don't bother me. It's all about the tone. Aside from some valve amps, even a lot of older 'lead sled' type amps aren't that heavy or awkward in the general scheme of things.
The price of some of these are a total bargain, especially considering most of the time, they flat out just sound better ( IMO, IME etc).