People put RVs on consignment because they don't like the price a dealer is willing to pay, and they don't have the time to go into the vehicle sales business on their own, or simply don't want to deal with the buyers.
They also make this choice because they want to sell to real, walk-in buyers, not telephone and e-mail buyers. Most dealers don't want to, either, which is why you are not getting the response you think you should get. It is hard enough to make a sale when the customer is on the lot, so few sales people think it worth there time to try to sell to a customer they haven't seen and might never see.
Some things sell easily by mail order, web sales, on-line auction, telephone, but RVs probably don't, or at least dealers don't think they sell that way. It is not quite the same as buying a DVD from Amazon, or electronics and optics in those situations where the buyer knows exactly what he wants and the seller has it in stock or can get it.