I imagine that a lot of people are going to want to inspect a device before they buy it, especially if the device takes user input. It's the same reason that the major console makers have their consoles on display in brick-and-mortar stores such as GameStop and the video game departments of Walmart and Best Buy: it makes the potential customers aware of the product and its capabilities and ergonomics. Sure, online-only sales are possible, but I don't see how an online-only strategy could attract a critical mass of customers to make the platform attractive to developers.
So today I went to Walmart.com and BestBuy.com and put each of these products into its search box. GameStick, Mad Catz Mojo, Nvidia Shield, GamePop, and JXD came up with nothing relevant. Archos GamePad showed up on both Walmart and Best Buy, but only as "ship to store: 5 to 7 business days". Then I tried GameStop.com. It drew a blank on Mad Catz Mojo, GamePop, Archos GamePad, and JXD. GameStick had "Release Date 9/30/2013". Nvidia Shield showed up out of stock online and 100 miles away in PickUp@Store.