Wireframes needs to convey messages about hierarchical structural of information without creating subjective options about aesthetics. As soon as you add color, shades of brush strokes, shapes that resembles real life objects, stakeholders are drawn into that subjects that they can reference to in real life. As a result, they are immediately sucked into reasoning that is tangible for them to digest, instead of focusing on matters that needs attention.
As a UX Designer, one of my best tools is wireframes. They are quick fast, and they help me create a hierarchical structure of information. This can then be shared, rearrange, updated or deleted with everyone input. Also, wireframes are not just for website. I use them to help me think through all types of problems.