When does a 3D model start becoming useful for the actual design process?

I have always found it interesting that a 3D model can start as something that just needs to represent the design, but then end up revealing things that weren't obvious in the drawings. You notice proportions, relationships between spaces, sightlines, and even little areas that feel awkward once everything is built up together. At that point it stops feeling like you're just making a visual and starts becoming another way of checking the design. For people who work with 3D regularly, when do you find it becomes genuinely useful beyond just showing what the finished space might look like?