I was introduced to the wonders of the internet in 1989 ...
Dealers probably had a culture, Back In The Day, of just keeping parts until they sold, the price would slowly increase over the years & hopefully recoup the cost of storage (plus also hopefully creating a repeat customer).
Was different between brands too, I could’ve bought a new plastic trim piece for a 1968 Volvo 142S in 2004 because that was before Geely bought Volvo and they had a culture of providing parts for enthusiasts to maintain their cars ... I was able to buy 1982-1985 spec plastic/rubber beltline mouldings for a car never sold in this country through the local Volvo dealer in 2003, manufactured by a Rare Spares equivalent in Germany as it turned out. But I think every manufacturer‘s dealers really only carry parts back about 10 years these days ... Benz and Porsche were the two that supported their enthusiasts in the late noughties, dunno if they still do.