Marketing really hasn't caught up to the 00's Gender Revolution and is still operating on data assumptions from the 80's and 90's. This is why some shows get bad tie in stuff (Airbender got a toyline that didn't jive with girls, who were a big part of demographic) and some shows have to fundamentally alter their marketing to make them palatable to kids (Adventure Time tried to sell Princess Bubblegum, LSP, and Marceline toys in pink packaging... boys wouldn't buy them because of this, even if they wanted the toys). This is why a lot of shows have started focusing more on stuff like T-shirts and high end vinyl figs: it costs you practically nothing to stick a design on a shirt and you can get new designs out in days if you need to, while vinyl figs go for a premium.
This doesn't mean that some shows still aren't having trouble with marketing. MLP: FiM makes tons of money from toys, clothes, and figures but it's a very firmly divided market between what the young girl fans want (ponies with hair to brush, pink dolls) and what the older fans want (show accurate figures, t-shirts, stuffed animals). Part of the reason why Korra got pushed to digital was to be able to use more adult oriented ads that they couldn't air on the channel proper without getting calls. Some shows, like Gravity Falls, have basically no merchandise and short runs despite massive views because their owners don't know what to DO with them. And some shows (like Metalocalypse) simply don't make enough period to keep them going because the network isn't willing to go in deep for stuff that fans actually want (full length albums, metal style shirts, more live shows).
