Succubus cheese is considered a rare delicacy and is traded like a black market drug.
All bodily fluids of succubi and incubi are aphrodisiacs because that is an important part of their feeding process. It’s important for them to be able to arouse their prey quickly so they can siphon off the sexual energy. In most cases, this is done with only a trace amount of sexual energy in order to ensure that they are able to feed far more energy than they devote to the feeding process.
The milk is different. Like any other mammal, milk is primarily used to feed the juvenile members of the species who are unable to hunt for their own food. This means that instead of trace amounts of sexual energy, succubus milk is highly concentrated with sexual energy.
Because of the energy expenditure involved, succubi are rarely willing to offer milk to anyone who isn’t a child they are trying to feed. When they do offer milk to anyone else, it is typically to domestic “livestock” as a reward.
As a result, for normal humans the milk is both a potent drug and extremely rare to find outside of a succubus harem. As you might guess, that makes it a highly valuable product. Technically legal in many countries, but pretty much impossible to get outside of the black market. Rendering it into cheese is used as a way to preserve it for transport and methods have been perfected to increase the aphrodisiac effect.
It’s typically only consumed in small amounts by the rich and powerful of the world. It is also sometimes used as a reagent by industrial scale spellcasters. Succubi and incubi do find the practice offensive, but since it is more important for them to stay camouflaged from vampires (their natural predators), they will rarely do anything about it. The exception is if a supply chain is traceable back to the location of a particular succubus.
Occasionally, someone will attempt to take a succubus prisoner to farm the milk. This rarely proves sustainable long-term because it is impossible to avoid the mental effects of repeated exposure to a succubus and local succubi and incubi will move to aid their escape.
Vampires have successfully farmed both succubi and incubi, but they typically concern themselves with blood products. They do have a method of fermenting clotted blood (both human and succubi/incubi) which is similar to cheese. However, they will typically prefer to feed directly from their prey instead of more esoteric products. Blood cheese is only marketed among vampires as a novelty or as emergency rations for trips that would kill prey species.
Succubi/incubi are vampire’s preferred food source. They can eat anything that has blood and humans are the main staple of their diet due to a good combination of being plentiful, nutritious, and tasty. Succubi/incubi are both better tasting and more nutritious for them, but are much rarer and so become a delicacy rather than a staple.
Since succubi/incubi know this, they will do their best to camouflage themselves into the human population. If it was just a matter of them preying on humans, succubi/incubi would have no need to camouflage. Even if not every human would accept being a food source for them, the process is pleasurable enough that they wouldn’t struggle to find volunteers if they operated publicly. Succubi/incubi are typically not lethal in their feeding, so there is little chance of being actively driven out by human organizations (outside of some religious fanatics). However, since vampires will typically stalk human population centers, if a succubus/incubus starts operating publicly the vampires will be quick to know and they would become a priority target.
The result is that succubi/incubi need to balance being seductive enough to gather enough food while blending into the human population enough to go undetected. The normal method is to build a large enough harem to not need to seduce strangers at all, but some (especially younger ones not ready for kids) will stay transient to avoid leaving too many signs in one place.
Most vampires don’t have the self-control to not just kill a succubus/incubus when they find one. There is no such thing as them feeling full and they will commonly engorge themselves when food is plentiful. However, older vampires tend to have better self-control and are more likely to be able to keep the presence of mind to keep a potential food source around to stay fresh. A few have successfully trapped multiple succubi/incubi to act as a larder to allow them to have high-quality food whenever they want. This does, however, mean that they ultimately have to bring in even more human prey. The laws of energy loss per trophic level apply and so to keep the succubi/incubi well-fed enough to produce a steady supply of blood, it takes an order of magnitude more humans being fed to them to keep them healthy.
If the vampires gave a crap, they could theoretically have a large enough domestic stock of humans to allow the succubi/incubi feeding to remain non-lethal. But, they are usually amused at forcing the succubi/incubi to kill and don’t care about the humans. So, it is fairly typical in such situations to limit the food supply to the succubi/incubi enough to force them to kill the humans, and then laugh at their tears when they feel bad about it. Most vampires are dicks.
Written in response to this Reddit post.