I agree with the tactile argument. If audio systems are trying to simulate the sound pressure experience in its entirety, then IEMs fall short. For the OCD-fueled desire for accurate sound pressure reproduction at the human-world audio interface, I think IEMs are where effort should be focused. 50 year old audibility studies imply that the perceptible gains are marginal-to-none-existent, but who says that's always the point? ;)