Mr. Nash must not have been a model railroader. Lets face it, we want our layouts to include rooftop signs, advertising posters, billboards and exactly the type of urban clutter that he was lamenting in his poem. On a layout, outdoor advertising and signs not only identify many of our structures, they establish the era and locale we are modeling.
Signs also define a neighborhood.
You expect to see a gas station sign in an industrial area, liquor ads in the poor part of town and advertismeents for banks is a well kept business district. Where and how we use signs is important in achieving realism in our modeling. Large and dramatic displays for soft drinks, cars or other popular consumer goods usually face major automobile highways and bridges rather than lonely railroad tracks. Wish as we might, in the real world very little advertising is directed specifically at trains, their crews and passengers except near busy stations. Driving through a city or rural area and taking note of how signs and advertising is displayed would help anyone do a better job with the signs on their layout, no matter what era is being replicated.