To my way of thinking, the two words should never be connected. Why do they need a phone? How many emergency phone calls do children make? This is usually the line the children will use in order to make a parent feel it is necessary to purchase one. If that doesn't work it will be, 'all my friends have one'.
Of course they can't just have a 5 year old phone whose buttons are so worn you can't see them, no, it has to be a 'popular' model. This obviously can be translated as 'costly'.
There is no greater risk to children today, I believe, than there was when they needed to use a public pay phone. I feel by having a phone, they are putting themselves at a greater risk of being mugged.
I think the widespread popularity of phones among children is due to a good advertising campaign and spineless parents. It is okay to say, 'no' to your children.
If the child feels it is imperative he/she has one. Make them get a Saturday job and let them pay for it and all the credit they will use. Do not offer to help with the cost or credit at all. This way, the ball is firmly in their court, they will realize how expensive they can be not just to purchase but also to make calls. I suspect when they realize they have to work all day Saturday to afford one and they need to keep working just to be able to speak to their friends, the proverbial light bulb will switch on.