First of all, money is very important thing in everyone's life so with them you can buy whatever you want or get some services. Saying about teenagers, having money is really necessary for them because they walk very often so they need money to buy something on the street or in the cafe.
If it is not enough pocket money for teenagers, they should try work part-time to earn some money for their needings.
On another hand, part-time job gives priceless experience for future full-time jobs so it is really useful and everyone should try that maybe he will find it interesting or boring and change his mind.
In my opinion, teenagers should work part-time because it is really helpful to choose profession and earn some money for costs.