In the last few years I've created some of those Powerpoints, and have realized the value in them (not saying that all are valuable). I've been asked questions like:
- We're a year in to a data warehouse migration and have nothing to show for it. What happened, where do we go from here, and how much will it cost? - We'd like to outsource a call center, but don't know where to start both on the tech and process sides. Can you help? - We have a business idea, but know little about technology. Can you put together a plan, so that we know how much we'll need to invest? Oh, and can you design the architecture and tell us which cloud to use?
There's tons of rigorous analysis, interviews, and research that goes into answering these questions well enough that they can be trusted. Since it's primarily an exercise in critical thinking, mileage probably varies depending on who is doing the work. There are plenty of bad Powerpoints I've seen out there that don't move the needle or add anything new.