If we're talking knotting in ABO and bonding, there's a biological determinism baked in that writers can either lean into or fight against. The physiological 'claiming' aspect creates an immediate, primal link between characters that's beyond their control. That's interesting to me as a plot device—it forces intimacy, but then the real character work begins around whether they choose to accept that bond emotionally.
Some stories use it as a shortcut to establish loyalty, which can feel cheap. The better ones, like in L.C. Davis's 'The Mountain Shifters' series, explore the tension between the biological imperative and genuine choice. Does the knot create the bond, or just accelerate its revelation? The negotiation of power and consent after the fact is where I find the real substance.
Honestly, it gets overused as a one-stop shop for instant mates. I'd rather see more stories where the knot complicates things instead of solving them.