Another approach, which limits the need to explore self-referential issues, is to suggest that you don't need to know nonobservable entities exist to find it valuable to believe they exist. There are some cases where the cost of learning a law is simply too great.
Consider a case involving your only child. They are eying a thin beam over a deep crevasse. Protective instincts surge over you and you state, "Get away from that! You'll fall and hurt yourself." Did you actually mean the second sentence? It is well recognized that children will accept a statement issued with confidence more than they will accept one which accepts the possibility of being wrong, so you can maximize your value better by appearing confident. However, faking confidence is not an easy skill. It may be more valuable to actually believe your child might fall than to try to fake such a confident belief.
Likewise, consider the case where the child got half way out across the narrow beam before their confidence began to falter. You encourage them from the other side with, "Come on! You can make it!" Did you actually mean the second sentence? By the same rules as before, you can maximize your value by appearing confident, but faking it is difficult. Thus, it is in your best interests to actually believe you child can make it.
In both cases, the belief is of an unobservable. You have never seen your child fall into a crevasse. In fact, you've never seen them deal with this particular crevasse with this particular wind condition. You don't have a model of what your child will do. You cannot observe the information you need, because you only have one firstborn child (if the solution is to sacrifice the first one to science and then have another, I dare you to suggest that solution to a parent. Get a head start :). Yet, in both cases, there is value in believing a statement about the child's future, regardless of whether it can be observed. It is even possible to show that it can be valuable to believe the child can make it, or the child will never make it, in different circumstances!