Kids may need cell phones as emergency tools. Since kids always want more freedom, if you're kid has a cell phone, you can allow them to have their freedom, but also know their where abouts. You'll also have a way to keep in contact with them if plans change last minute. It might be unlikely that an emergency will happen, but all you need is one emergency to change everything, and make you wish your kid had a cell phone.
However it's very common for a kid to over use their cell phone. Make sure the parent sets boundaries, and consequences if those boundaries are broken. Make sure they know that the cell phone is a present, and that you pay for it so its your property.