In one sense it may be logical but a big part of model railways is recreating something long lost. I love BR steam/diesel transition from the 60s but I was born in the 80s. The ICRs do nothing for me personally (apart from being pleasant enough to travel on) whereas CIE Sulzer or E floats my boat. Different strokes and all that, but if we werent interested in the past there'd be no steam models for instance, no 141s selling in Black and Tan for instance. The age profile of the hobby is another thing to consider, people who can remember 121s in their heyday are usually those who have the extra income to buy them rather than young people who only know ICRs. But sure that's just my opinion!