Wherever you have a published template that you circulate to your customers/suppliers/employees and expect them to fill it in before sending back to you.
A few use cases spring to mind. Let's say I'm a recruiter and receive a CV from a client who uses a template. I could use this to pull out different parts of the CV in to structured data.
Another one, I could have a 'custom order' form for special requests that I give to a customer. They fill it in & send back.
An internal use case, lets say there's a certain word template used to produce documents which are then saved to SharePoint. I may be interested in taking those particular documents when they get saved/updated in sharepoint and pull out the structured data.