For me, wireframes are a tool I use to make my ideas less abstract to those around me - particularly when it comes to intricate layouts and work-flows. Wireframes are a quick and cheap way of expressing functionality, layout and interaction design. They can be a fantastic tool in communicating with your team as they allow fruitful design conversations to happen before anything is actually built. I've even used wireframes in usability testing and have gotten invaluable feedback from them. Another nice outcome of using wireframes early in the design process is that they can uncover engineering tasks early in the process allowing engineers to get started on inter-dependent back-end work. While this is going on, interaction designers can begin to design the front-end in parallel.