I don't know about "immersion" which I consider a laughable buzzword that gets thrown around like "metagaming," but depending on how a trap is presented and adjudicated by the DM, it can basically be just random number generation affected by whatever choices the player made during character creation. Whether anyone finds that fun is up to them.That's the thing, right? There's basically nothing interesting or exciting or suspenseful about the occasional trap going off because nobody's passive Perception was high enough. What's interesting is knowing the trap is there, coming up with a plan to avoid/disarm it, and then crossing your fingers that it works. And the problem with just "rolling to disarm" is that you know you're doing the correct thing. The optimal strategy, for the "use a skill" crowd, is to pick the guy with the highest bonus and have him roll. You aren't left wondering, "Is this the right way to do it? Should we have tried something different? Wait...maybe I'm not ready yet." And it's that wondering while you wait for resolution, whether or not there's a die roll, that adds to the suspense. A.k.a. "immersion".