Your product was designed to solve a problem. Understanding when this problem occurs is important because it lays the foundation for how often people are expected to use your product.

Airbnb helps you find a great place to stay when you go on vacation. People go on holiday once, maybe twice a year. If Airbnb looks at how many people booked nights every month, it might look like all their users have churned. 

If you think about the natural frequency of their problem, it makes more sense to look at how many people booked nights every year. What looked like lots of churn now looks like great retention.

Understanding how often people have the problem you help solve also plays into when and how you should charge them. It informs when to send them notifications and what counts as a useful update. If people have to solve your problem once a month, sending them emails every day will just feel like spam. On the other hand, a monthly reminder would be mighty helpful.

The natural frequency of the problem you solve is the bar you use to gauge what's too little and what's too much.