I don't know of one of my friends who got into mode; railroading because they went to a train store and said "Gee, I should buy a train set."
Most got into it after seeing someone else's layout. My Dad got into it when I was younger (10-11), why? Because a friend of his Uncle's had a layout in the basement. He lived in Hamilton, Ontario and had modelled the Hamilton harbour and Steel Mill route at one end of his basement and the Toronto Union Station and train yard at the other, with a couple of small stations and farms in between.
Then we went to a train show to get some other ideas, then to the Toronto Model Railroad Club on Hanna Avenue. My Dad was never one to join clubs, but he went once just to get ideas. Then he looked in the paper (no internet in
1965) to see if anyone had train stuff for sale. Ended up buying 2-3 boxes of stuff from a woman who's husband had passed away and she was selling his layout.
It was only AFTER he had his benchwork done and started laying track they he went to the local retailer to get more stuff.
Most people I have talked to got in the same way. Saw a working layout, went to a Club or Train show, then to the retailer.