Well, it is plain and simple, Gengar is a ghost Pokemon, and Ghosts = Halloween get it
Its a wonderful illustration brimming with the artists creativity
Even in a depowered deck, you can find Salt Marsh, Jwar Isle Refuge, Frost Marsh, and Secluded Glen to make the other colors in a deck built around The Mimeoplasm or something
That's a great creature
Collector Boosters are the best way to collect variant rares and mythic rares, as well as traditional foil cards, and they're the only place to collect foil-etched and extended-art cards
This leaves the opportunity for the USA people with contacts in Japan to tap this resource of loose raw cards to then grade them with CGC and then evenly spread them across all the selling platforms (limiting the supply impact effects on the market liquidity as much as possible, not swamping any one platform)