Age of Ultron
In the lead-up to "Avengers: Age of Ultron", Joss Whedon explained that despite bringing Phil Coulson back to life to helm "Agents of S.H.I.E.L.D." and the MCU itself dealing with characters seemingly dying only to return later on like Loki, Nick Fury and Bucky Barnes, "As far as the fiction of the movies, Coulson is dead", choosing to not reference Coulson's resurrection in "Age of Ultron" to not diminish the impact of his original death amongst the characters. Whedon further elaborated that due to his feeling that the audience of "The Avengers" doesn't necessarily seem to be the same one as the audience of "Agents of S.H.I.E.L.D.", in addition to introduce nineteen new charactes, he would have been forced to explain Coulson's resurrecting once again to the film-only audience had Coulson been featured in "Age of Ultron". Despite this, Jeph Loeb stated prior to the film's release that there was a plan for the Avengers to discover that Coulson was alive eventually.