One of the reasons to hire an architect is to help you see what can be. For some people, it can be hard to imagine what something might look like from a set of plans. They see the plan and they can understand the room sizes, but picturing what the effect of various decisions can be hard for most people to see.
In working with homeowners, I have seen where they will sometimes say: "I want to add this space here and then move this wall here," and other things. Often, I have to spoil their enthusiasm by explaining what the effect of those decisions will have on the three-dimensional aspect of the design, and often, the increase in the cost of the structure due to these choices.
This is one of the reasons why as an architect, I try to show as many 3D views (renderings) as I can to my clients. When people see the world, they see it in 3D, not in plan, not in elevation. By doing this, they can 'SEE'.