If I were arguing the opposite point of view, I would say that inspiration from fiction is a romantic starting point, but that travel guides are much more than just a sub-part or a supporting tool; they are often the first concrete contact with the feasibility of a trip.
The problem with the idea that fiction is the main source is that it ignores how people actually discover places.
A guide can present places or activities that one would never have imagined, well beyond what a film or a book could suggest, creating desire.
For example, my friend discovered the Marolles in Brussels, a charming neighborhood, not in a novel, but by flipping through a guide on flea markets, proving that the guide creates inspiration.