Why are bats mitzvahs held?

Answer 1

A bar mitzvah is not performed. A Jewish boy becomes bar mitzvah at age 13, regardless of whether there is any ceremony. (The term for a girl is bat mitzvah.) At this age, a boy is, in the Jewish tradition, considered to be responsible for his own actions and able to be counted toward a minyan (the quorum of 10 required to hold public prayers) and to lead public prayers. It's traditional to hold a party to celebrate this, starting with a service in which the new young man actually leads some of the prayers to demonstrate that he is ready to take on this obligation. A party follows, and by the middle ages, there were rabbis who said it was worthy of the same kind of celebration you'd hold for a wedding.