The main reason being size and weight. The more material there is, the heavier the doll gets. And it get's pretty heavy as it is 100% dead-weight in the full-grown body size. Also, as the doll grows the amount of material used increases, thus the doll’s price increases.
A lot of our customers may have limited storage space, are older or need to hide their product from others. So, having a smaller doll is convenient.
At the same time, we're aware of concerns about illegal sexual activities and we fully cooperate with local laws. Please remember that these products were designed to fulfill companionship needs. We are in no way marketing, implying, nor condoning any illegal sexual activity.