The low-middle range motels I most often use have plenty of space for parking big rigs. Much of their clientele are work crews, having big trucks pulling trailers and other equipment. Super8, Budget Inn, Sleep Inn, Econolodge for example. Motel 6, however, tends not to have this extra parking space.
If there is any mention of roomy parking space, it will be listed as truck parking, rather than RV parking.
As I go higher on the price scale, there tends not to be as much truck parking. I suspect per diem for these mobile work crews tends not to be generous enough to cover $90-150 per night motel rooms.