Well, you're asking about the fetish element, but the themes people actually dig into with it go way deeper than just the visual. I've seen it used as a metaphor for a character's secret, overwhelming power or a desire they can't fully hide. In some of the stories I've read, the 'bulge' isn't just a sex thing; it's about the anxiety of being found out, the shame mixed with a twisted pride. The tension isn't just sexual—it's about a character wrestling with a part of themselves that society tells them is wrong, but that feels intensely, uniquely theirs.
That internal conflict drives a lot of the emotional core. You get characters who are maybe in positions where they have to present as one thing, but this physical truth betrays them. The fear of rejection if someone sees it, but also this desperate, hungry hope that maybe someone will see it and not reject them. That push-pull between concealment and revelation is where a lot of the best drama happens. It's less about the act and more about the unbearable vulnerability of being truly known, in every sense.
A lot of readers, myself included, come back to that specific dynamic because it amplifies every other emotion. A moment of tenderness becomes heart-wrenching if the character is terrified their partner will feel the bulge and pull away. A moment of passion is charged with the relief of not having to hide anymore. The physical detail becomes a lens that magnifies intimacy, fear, acceptance, and taboo all at once, which is why it sticks in the mind long after the story ends.