Because prevention is the best way to prevent diseases..even you have a cure to your disease but there are possibilities that the cure has no effect..
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Prevention is betterĀ  because you wont be spending or if you spend it is less expensive and you wont be suffering from a disease, than when you have to cure yourself from a disease which means you are already suffering and you will be spending more for the medicines, the fee for the doctor and the worse if you are hospitalized you will be paying more
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