The willingness of a user to evangelize is tied to wow moments more than the total value.
It's possible for a tool to deliver lots of value but with lots of small savings constantly.
That's a product that a user might love and be unwilling to give up, but probably wouldn't actively evangelize to their friends.
Contrast that with a service that has the same amount of value, but more spiky.
Rare spikes of standout "wow" moments.
Those wow moments are prominent, easy to describe to others, and hard to ignore.
That makes them more obvious to evangelize to others.