I think it's similar to collecting old guitars; people in their financial prime buy a connection to the music and bands of the 60ies and 70ies; their children may have grown up with electronic music and can't relate.
Cars might be relatable, since you can still drive around with it, but the current fashion of having 'vintage' things may be over in 10 years.
Following this trend, Model As and Ts have gone way down, as the dreamers are now past the age or dead.
57 Chevys are on the downside, too. Too old.
90s Japanese sports cars are on the upswing now.
But stamps? I don't see it recovering. It was popular in the 70s/80s, like Professional Bowling. Both are still with us, but not the same as they were.
In Canada, I think it’s 17 years of age, then you can bring in your right hand drive car more easily than container of potatoes.
Personally, I don’t know why each country has its own safety standards when every industrialized country has a similar enough mix of speed limits and urban/suburban/rural environments.