Well let's be clear, Dragonite hasn't been truly marketed outside of a few merch examples (the primary example being about Ash's Pokemon). It was primarily Dragonair that was heavily more focused on and Ash only caught Dragonite (sure it evolved from Dragonair, but still you'd think they would have pushed Dragonite a little bit harder than I guess until after he caught it, in which more and more merch was about Dragonite over Dragonair but it did primarily feature Dragonair prior to capture (or revealed merch)
My point is, I'm pretty sure we've had some Chandelure merchandise (I think there was at least one or two that showed Chandelure, like a toy that was with Lucario/Dragonite I think), but no Litwick or even Lampent, so I don't necessarily think it matters if there's no Litwick or heavy Litwick merchandise. Because capture or not, it still would be marketed and yet its not, which is otherwise bizarre, since I'm pretty sure most of the Pokemon being marketed aren't even going to be relevant anyway so why not have Litwick merchandise anyway.
Of course it's possible they are keeping some merchandise hidden as well. Kind of like "Satoshi Kurumiru" or "Ash's Sewaddle" and how it didn't have any merchandise outside of being known for being Ash's Pokemon (aka no Sewaddle merchandise at that time), and how there was a debate as to whether or not Ash was actually going to catch Sewaddle, and I was convinced because merchandise was leaked, but people disagreed thinking it was fake (or rather a typo). But it turned out to be real, Ash did in fact capture Sewaddle.
So there may not be general Litwick Merchandise, maybe because they want "Satoshi Hitomoshi" merchandise and want it to come out when he actually catches it (like what they were going for with Sewaddle). Perhaps even general Litwick merchandise is being hidden, perhaps they just want ONE thing to be hidden for one of the team members, and they figure Ash catching Litwick will be extremely "shocking" and out of the blue, and want to capitalize on it. If only because if Ash does then capture Riolu/Lucario, they probably aren't going to keep that as hidden.