Unlike many others here, BR blue was not a feature of my childhood; the locos I grew up with were 3/4 scale versions of EMD and GE products. So that kind of nostalgia is not a factor.
Price and availability means most people over here model either the UK or US scene. When I was 12 I got a Hornby Flying Scotsman train set, and for years after, I was only interested in things LNER. As I got older, I gravitated more towards diesels. I like the Blue period because, colour aside (and I think the colour is actually a really spiffy bit of design), it was a really diverse era: I'm mainly interested in the 1970s period, and so much was happening in this time. TOPs, headcodes, no headcodes, three different marks of standard coaching stock by the latter 70s, a fair bit of pre-nationalisation NPCCS and the odd buffet knocking around in blue/grey, heaps of different classes of loco and unit, each with their own geographical sphere...
The Blue railway, for all its problems, was still a real railway. Locos hauled passenger trains, and range of freight still travelled by rail. Loose-coupled unfitted freights and revenue earning HSTs coexisted for a while. Blue provided the impression of a cohesive railway network with a bit of permanence. There is a lot of scope for things in the Blue era!