Is it illegal to be out past curfew with someone 18 or older? And why?

Section 11-1-3 of the Town Code for Camp Verde provides: A. It shall be unlawful for any juvenile under the age of eighteen (18) years to be, remain, loiter in, about, or upon any place in the Town away from the dwelling house or usual place of abode of said juvenile, between the hours of 10:00 o'clock p.m. and 5:00 o'clock a.m. of the following day; provided that the provisions of this section do not apply to said juvenile when: a) accompanied by his or her parent, guardian, or other adult person having the care, custody or control of said juvenile, or b) the said juvenile is on an emergency errand, or c) the said juvenile has been specifically directed to the location or is on reasonable, legitimate and specific business or activity directed or permitted by his parent, guardian or other adult person having the care, custody or supervision of said juvenile. This exception requires that the parent, guardian, or adult have advance knowledge of the whereabouts of the juvenile, and have given consent, and does not apply if the parent, guardian, or adult, when told of the location of the juvenile, does not object. B. It is unlawful for the parent or guardian of a person under the age of eighteen years to permit such minor to be away from the minor's dwelling house or usual place of abode in violation of Section A once the parent or guardian has been notified of the violation and permits repeated violations. C. Curfew is extended until 12:30 a.m. on Friday and Saturday. In short, your parent can be responsible for you. Curfew begins at 10:00 p.m. on Sunday-Thursday and begins at 12:30 a.m. on Friday and Saturday. And by the way, every person under 18 (and every person over 18 hanging out with someone under 18) should be aware that sexual relations between someone over 18 with someone under 18, even if it is consensual, usually results in a very long prison sentence (often more than 10 years) for the person over 18.