Something you may not have noticed in your travels: the disappearance of “Vacancy” signs. Fewer and fewer motels and hotels display them. Travelers these days can use a smartphone app to see what lodging is at the expected destination and can call ahead to check on availability.
Fewer mom-and-pop motels exist; chain hotels, as in other industries, are more prevalent. The chains don’t want to advertise that they are full. They want the traveler to come inside, so if there is no room at the inn, they can be directed to a nearby property operated by the same chain.
If you are planning a motor trip, RoadTripUSA.com is an excellent resource for traveling off the interstates. Or you could buy the book.