Openflow Proactive versus Reactive flows

As per my understanding;

• Reactive Flows: When a new flow comes into the switch, it looks up in the flow tables. If no match is found, the switch sends a Packet In packet to the controller to find out where the packet should be sent (the resulting broadcast message will update the correct location of the designation once it is found).
• Proactive Flows: The controller can populate the flow table before any packets have arrived. So that all traffic matches that come into the switch will be able to be forwarded at line rate and not have to go through the Packet In situation.

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My question is what are some real world examples for these two methods?

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I can understand that proactive will be faster and great for static networks, and possible for limiting certain traffic via ports and protocols i.e firewall applications. However, reactive I can only really see it being used in networks that will experience unknown traffic/clients. Am I missing something?

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Sorry if this post is not allowed, If I could be directed to the appropriate location that would be very helpful.