I thought the same. Then I realized that without a phone, teenagers will be left out of a LOT of social planning and notifications.
As a YM leader, I found that the boys who didn't have phones were left out. Other boys couldn't get in touch and the parents were a disconnect--they'd forget to pass along messages, etc.
My take is that there is a proper balance that takes a lot of parent involvement and supervision, but that phones are an important part of positive social integration now.