It's really a fund controlled by the current "grandparent" generation. They do use it on themselves too. The current generation has used it to do river cruises in Europe. The previous generation used it to realize a lifelong dream of going to Antarctica. But a lot of the gains get allocated to the rising generation at critical points in their lives. Often in the form of a UTMA/UGMA that gets a big batch of funding when a new child is born.

The UTMA/UGMA can be used for missions, marriages, college, homes, etc... without depleting the principal.