Three typical situations I work with.
You have deep knowledge of a specific industry — logistics, fintech, healthcare admin, education. You see a problem others don't, because you live with it daily. The product idea has been turning in your head for a year or two. But — how do you get from "idea" to a plan you can actually build against? Discovery brings structure: where's the hypothesis, where's the fact, what's worth building, what isn't.
You have an offline business that needs digitalizing, or an idea for a product on top of your existing one. The question is — what to build in v1, what's a realistic scope, what it'll cost, who should build it. Discovery gives you those answers as a document you can take to vendors — or even to investors.
A corporation, agency, or startup that wants to launch a new line — either a B2B service built on existing expertise, or an internal tool that automates a routine. Discovery gives you objective research on the idea and a concrete product brief the team can start building from.