Maybe it's because anti-orgy is politically correct back in the day, considering sexual gathering of three or more is still illegal and punishable by imprisonment today, but since wuxia genre started, "harem-type" stories have always been around, and have been popular online, but IRL, only "pairing-type" stories are allowed to gain fame, and made into shows, like Jin Yong's, etc., but harem has always been around