OData, to me, makes sense for data that has a dynamic schematic and/or a client that wants to explore or wander the data in the way an intranet or analyst does. Like Excel folks might. Not the way a phone app or desktop app might. Great for a certain kind of app.

For narrower apps, I'd make a web api but consider using just the OData query string formats (filter, sort) for flexibility.

In short:

Internal API = OData (= data layer)

External API = WebAPI with OData methods (=service layer, which brings the endpoint data to 3rd parties)

And because it's an internal API, it's a reason why you don't see it a lot in public API's (SAP uses it intensively though)

Thanks :)