Once again, laziness.
Bioware claims to be truthful and honest towards its fanbase and blatantly gets lazy with ME3. That's why the RPG factor is so dumbed down, also why the side quests are such boring chores, and the ending was utterly crap even with the EC endings. Still felt half-assed.
the concept itself wasn't bad, it was the execution and how it was presented. Had it been well thought, a 30-minute section which completely summarized the difference you made, that would have been great. I just wished my choices mattered, but they didn't. The only difference in EC is a slide or two.