Because it doesn't make sense. The game is constantly being updated, and accordingly so is the Nude Mod. Buying 20$ Tier on Patreon you get all animations, Nude Mod and the game all together. You don't need to buy every month if it's a lot for someone, once every six months or year is enough. The game goes public every month anyway, and I really need "constant" financial support much more than a year ago.