The benefits of giving a child pocket money are various. Giving your child the lesson of the value of money means they will learn that what they have in their pocket is there to spend but once it's gone, it's gone and they will have to wait until the next pocket money day to buy anything else. They will learn to understand that you cannot have all of the things that they want all at once and this could be a valuable life lesson.
Having this power will also teach your child the concept of saving. If there is something that they want, they may have to save for it and it will teach them discipline with money.
There are cons to this though, your child will have the power to spend that money on what they want when you are not there so you will have to set rules so that this does not happen. It takes away the parental control of being able to decide what your child is exposed to, whether that is toy guns at a young age or alcohol at a much older age. There is also the willpower factor where parents are concerned. The pros above will not work if you do not keep to the payment dates. If you give in and give pocket money early, this will not teach the value of saving or waiting.
You may want to think about the age of your child, where they will spend the money and what you will still buy them once they have pocket money (do they buy their own clothes?).
There is an argument here and an expanse on the above will give you the answer to what is right depending on the family situation and the type of child.