This is a great question. Let me give you a historical snapshot and give you an explanation of why rites of passage are important.
In 1909, the French anthropologist Arnold van Gennep came up with the phrase "rite of passage." He saw that rites of passages were all over folk literature and life. He argued that these rites of passages were important for people in times of transition. In other words, it makes these transitions in life easier from a social point of view.
He use the Latin word limen, meaning threshold, to make this point with the terms preliminal, liminal, and postliminal.
If you think about this insight, it show us why rites of passages are important. In all cultures, there are times of transition or change. When these times happen, it is hard for the individual and the community. Therefore, to mark those times with rites gives a fresh understanding to the one going through the transition (a new identity) as well as those who are witnessing it. In this sense, a person is reintroduced into society as a person in a new stage of life or situation.
For example, a Jewish boy becomes accountable for his actions at the age of 13. This eases the child into adulthood.