Technical overviews are useful to obtain the 'big picture' of the technology of a entire field. What kind of solutions are used or will be used in the future.
Technical overviews via patent search are important when planning a new project area. It’s possible to find out who the competitors are, what kind of technology they have, and what the markets are, where they are going to become active.
Beyond that, technical overviews can be the basis for very effective brain storming sessions.