In their design and marketing, motels attempted to appeal to both the traveler's desire for adventure and need for security. As automotive technology allowed people to travel further from home and increased the numbers of people traveling, the preference for security -- namely in the form of standardized accomodations -- won out. The story of the motel's evolution in America is remarkably similar to that of those other roadside institutions, the gas station and the restaurant.
As with the gas station and restaurant, this story is not strictly chronological nor is it national. Accomodations varied greatly region by region. Those states which could support year-round tourism, such as California and Florida, generally had larger and more luxurious facilities. The growth of the motel was not the result of a corporate marketing plan; rather it was the response of local entrepreneurs to local demand. And that demand was great; a 1933 article in Harper's magazine quoted the (then fledgling) AAA statistic of "30,000 tourist cottage and camp establishments [making them] one of the few features of the American landscape that the depression is causing to grow by leaps and bounds" (McCarthy and Littell qtd. in Flink, 185).
It would be a mistake, however, to view these accomodations simply in their role of money makers. Tourist camps and motels became institutions, and during the Great Depression, America sorely needed functional institutions. Warren Belasco explains, "At a time of class unrest, the road seemed to bind people as playground and symbol...In the long run, this depression image of democratic congeniality and remarkable business success won still more middle-class converts to tourist camps and served as a useful public relations theme for the automobile industry" (Belasco, 145).
While the motel was far more affordable than most hotels of the day, those who could not afford its modest fees were obviously excluded from staying. The motel developed out of a tension between inclusive democracy and exclusively middle-class homogeniety, between the desire for novelty and the need for predictability, between the traveler as independent adventurer and the traveler as consumer. You can follow that development from the motel's early days as a campground in the late 20s, to the early chains of a mere decade later.