Honestly, a lot of it comes down to the biological imperative baked into the subgenre's worldbuilding. The knot is the physical, undeniable proof of the mating bond, and for readers who crave that level of fated certainty, it's the ultimate payoff. It's not just a spicy detail; it's the culmination of the 'mine' claim made manifest. It forces a period of intense, inescapable intimacy that can be used to break down emotional walls or heighten vulnerability right after a climax. From a narrative tension standpoint, it traps characters together—literally—which is a gift for authors looking to squeeze out more dialogue or emotional revelation when guards are down. I've seen it used brilliantly in dark omegaverse to underscore themes of possession and loss of control, and in sweeter stories to emphasize protective, caring instincts. Without that anchor, some scenes might feel like they're missing the final, irrevocable seal on the relationship.
That said, I sometimes skim past overly clinical descriptions of the mechanics. When it's woven into the character dynamics instead of just being a checklist item, that's when it truly matters.