Jonathan, I am sure your observation about the modelling aspect of large prototype layouts seeding the RTR market and enthusing other modellers to 'give it go' is happening more than ever.
In my opinion the biggest single factor in all of this is the internet and particularly this website and similar forums. Without it, where would we be seeing these magnificent layouts, modelling techniques, sharing knowledge, friendly discussions, photographs and diagrams and so on. There is only so much that the model press can portray and exhibitions cannot show those 'stay at home' layouts. In the past modelling was probably more localised with modellers meeting and discussing railways with friends and acquaintances in their nearest modelling shops and visiting exhibitions that were in a limited mileage of their home town. The use of the internet has without doubt expanded the model railway scene.