When should you actually use Redux; given you can manage all your state in a top level component? Where do you draw the line?

I've worked with Redux for some time now. I fail to see the hype around Redux being given prominence even while building a fairly low-level complexity apps, like a phone-book web app.

Personally, as a React/Redux developer where do you draw the line between; "Yes, this app can do with having the state in a top level component" and "Nah, this app is complex enough that it needs something for state management ala Redux"?