It isn't a surprising question, it's asked often. I wrote a post before called "Yeah but". That's the kind of response that often comes after answering the question with, "Yeah, you should".
"Yeah but... the architect isn't using Revit, the engineers aren't using Revit, we don't really need 3D for this project, this project doesn't have the margin, this project is fast track, this project isn't big enough, this project is too big"... and so on.
A recent one I heard was, "The architect isn't using Revit, should we use Revit MEP for this project?"
When Revit Systems was released in 2006, the essence of Autodesk's marketing commentary was, "this is new software so it probably doesn't make sense to tackle a project with it unless the architecture team is using Revit too." I don't think it is still true six years later. Sure we benefit from the modelling effort in architecture and structure but we can still benefit from the effort without them.