On the larger game teams I've worked on, most people using blueprints and schematics aren't the programmers but the content creators. The programmers are providing said blueprint elements/building blocks as well as extending (or modifying) the engine with other logic that content creators don't need access to via their visual tools.

For example: a level designer might want a specific type of entity in their level (let's say a floating platform). A programmer can extend the engine to provide the logic for said entity, which accepts parameters like how quickly the platform should move, what should trigger the movement, in which direction it is moving, etc. The programmer implements all of this and the final result is a new entity type said level designer can drag and drop into their level in the editor, and configure to their heart's content.