They're printing other mons because its less appealing to buy a set that's 20 cards so they need fillers which is where many mons always end up, the last useful castform was holon's castform, apart from that castform was used for filler in the D/D/P era due to its forms allowing it to take up 4 spots and now in S/M its getting its first new print, Dewgong wasn't printed at all from HGSS(2010)-Generations(2016). As seen with Garb, Blastoise, Shaymin Sky, All the Nightmarch mons and so on, pokemon that aren't huge marketing points can be made marketable if they have something to market in the first place. Shaymin Sky a pokemon that had next to no presence in the tcg was given 1 ability that made it the definition of important support card and has become the most expensive card for deck building and even was a main reason behind RS getting another printing run. Tying the TCG releases to whats going with the games is the best way to keep the tcg going, it gives a core idea for a theme of the set then it goes from there. Excluding X&Y theres always been a visual change with a new generation of games released signaling a movement in the franchise the blanks becoming more modern and sleek the same way the games are looking better and the graphics are smoother, each movie always has a set to tie loosely with it. Legends Awakened, Arceus, Nobel Victories to name a few. All of that is tied to the franchise moving ahead. As to why there's another charizard box being released when next to no one wanted or bought the last EX box is not only ridiculous but annoying when Charizard's GX spot let alone box could be used for any pokemon with any type of playable asset. To this day apart from base set charizard (even that is a bit of a stretch) I cannot remember an actually viable charizard card. Its a pattern of Throw charizard on a card high damage attack with high energy cost with a draw back that is not worth it: Charizard ex, Charizard *, Charizard G lvX, Charizard EX, both M Charizard EX. By constantly printing a charizard every time a new gimmick comes out (there has been one for every gimmick excluding Light Pokemon) it takes a gimmick spot away from a pokemon that hasn't been printed often enough, something viable or something new or innovating 5 energy for 200 damage to do 50 in recoil and discarding 10 cards from your deck gets super stale quickly
