Like Rod said, in this era of plentiful models, many forget there was a time when product availability was nowhere near as extensive. If you wanted something unusual or something you couldn't afford, you made it out of whatever was available.
Having started out with my trains in that era, I've got to laugh at the arguments and whining these days about placement of some piping or headlight positions on our new products.
I had wanted one of the New York Central powered commuter cars that I always saw while trainwatching around the New York City area. My father found a powered diesel truck somewhere and adapted it to a Lionel heavyweight "Madison" car, and I had my commuter car.
Realism was secondary to the satisfaction of having a unique model running on the layout. I've always appreciated these one-of-a-kind creations. If we could only know the whole story behind their imaginative creation.
Jim