It can be difficult to explain why some people respond sexually to things that are not obviously sexual, such as pretending to belong to another species than your actual species (which is one way of describing pup play, although there are also people who pretend to be horses, or other creatures). I could legitimately ask what that has to do with sex. Yet it evidently does.

Part of this can be attributed to Pavlovian conditioning. Just as a dog can be conditioned to salivate when it hears a bell ring, so can a person be conditioned to be sexually excited by almost anything. For example, if you have an orgasm while you are tied up, then that creates some connection in your mind between having an orgasm and being tied up. And the more times you do this, the stronger the connection will become. It is possible to reach the point where you can only have an orgasm while tied up. Kinks tend to be self-reinforcing.

However, it is not all Pavlovian conditioning. There are ultimately deeper reasons for any given kink. For example, I am sure that there is ultimately some socio-biological basis for the sexual practice of dominance and submission, in the sense that these have been used as reproductive strategies and therefore become part of human evolution. It may be that those who can dominate others, and those who are willing to submit to others, both increase their chance of reproduction (despite the fact that nothing on the gaykink sub-reddit involves reproduction).

If you don't mind my theorizing for a bit, I also think that a sexually repressive society, in which people are made to feel guilty for having sexual desires, tends to push people in the direction of dominance and submission. Dominant people have been convinced on some sub-conscious level that sex must involve some (actual or symbolic) coercion, because sex is obscene and therefore people will not willingly consent to it. Submissive people have been convinced on some sub-conscious level that they are not supposed to consent to sex, therefore in order to have sex they must be coerced in some manner.

However, if people are asked why they engage in dominance and submission role playing, they will almost never offer those kinds of explanations, they will just say that it is hot. Most people never want to go beyond surface explanations - nor do they need to, of course. But perhaps since you are looking into this from an academic perspective, you might want to think about deeper explanations. Whether any of this is worth mentioning to the people whom you will be teaching about kink culture, I cannot say.