A Catholic is baptized and has their confirmation. People who practice Reiki will ask each other what level they have reached. It seems everyone around the world is doing it. It is a recognition by those around you of the progress you have made, another entry on your spiritual resume. Yet it is more than the outward signs to the people you practice with.
Initiation is also more than just a box to be checked, more than just a single destination.
A Catholic gains a new name in addition to the old one, a shaman is given a completely new name, a Wiccan Priestess is considered to be a new member of the craft or coven, and students of the mystery schools are washed clean and taught new things. The old person is gone away, and in their place a new person stands. When a person is initiated, they gain access to greater degrees of the mysteries that are taught. A priestess will be taught some of the greater ways only when she has shown her dedication to her path. A similar thing can be said of Druids.