I think I get what he's talking about. It's silly, but it kinda makes sense. He's blaming the retailers for not carrying large stocks. Let's say you're Best Buy (I know nothing about Best Buy's retail practices, this is only an example I'm probably wrong, but work with me.) You have a set are for all your video game items. In this case let's say 4ft long, 4ft wide, and 2ft section for 3DS(low middle high). Now each 3DS box is a 6in long maybe an inch thick/high or so. With such limited space you're going to place a few units and then use the rest for it's games and accessories. If you had 25 colors there's no way for you to fit all the 3DS on the shelf. You're going to put only a few there and the rest in the back. Now here's where I think the problem lies. The space they have for such inventory is just as limited. Of course when you have 25 colors you're going to have more than one of each color. You then realize they have other products they're not willing to allocate precious backroom space for that many units of so many colors. They have other items they sell and want space for those as well. Another point is that they (retailers) look at sales. If you had just four colors and one out sold the others, the store will gradually purchase more of that single color. Much like everything else, they go with what's popular rather than worry about variety. At best they'll order the popular color, the basic color, and probably the 2nd best seller. So the short answer is that retailers aren't willing to devote themselves to selling all the colors since space is limited and sales don't show enough warrant more variety.
Simple answer is indeed for them to sell them online or directly from the manufacturer. The first might be easier, and the second may not make those retailers too happy. Pretty much cutting into their sales they would normally see. What would be the point of sending to the stores if they're going to do it themselves? At least that's what I think. I'm no expert so it's seems a logical conclusion.