Do you think Legends will be getting DLC in its place?
It's not so much that they're ignored as it is The Pokémon Company is legally a separate entity from Nintendo. (Nintendo is a co-owner of it but not the sole owner.) They get the last word on what to do with the franchise. If they want it on a separate video, that's how it's going to be presented.
My best guess as to why it's done this way is because the presence of Pokémon as a franchise differs from the presence of Nintendo in general in different parts of the world. There are places where Pokémon is quite prominent but Nintendo is near invisible, such as Southeast Asia and the Middle East. In those regions, a Nintendo Direct isn't going to get much attention, but a Pokémon Presents would. (As to how that can be the case where people don't care much about Nintendo but eat up Pokémon stuff, most such regions have a focus on the mobile games, the anime, and the card game, though there are a few areas, like Russia and Brazil, where Nintendo systems are bought solely for Pokémon games, with all other Nintendo system exclusives falling by the wayside. They don't care about Mario, Zelda, Fire Emblem, or anything else on Nintendo systems there. Just Pokémon.)