Why are the creeds important in the Catholic Tradition?

Because the Christian Church, in particular the Catholic Church is not "Nondenominational." This is to say the Catholic Church actually believes in something and in someone; (Jesus Christ) It is not an "anything goes" free for all in the Catholic Church when it comes to Faith and belief. Being Catholic means something; it is not just a name.

The creeds are short statements which summarize the main tenants of the Catholic Faith. The creeds are so fundamental and foundational to the Christian Catholic Faith that to deny them is to place yourself outside of the Faith. The Nicene Creed is recited every Sunday in Catholic Church's precisely because a creedless Christian Community is an oxy moron.