How does the state select people to get jury duty notices?

So I’ve been summoned for jury duty on Sept 20th. This will be the third time I’ll have to appear for possible selection in the (less than) six years since I’ve turned 18. On the other hand, my mother has never been called for jury duty in her life. How is this possible? How in the world can I be called three times in less than six years and her not at all?