A juul vaporizer does last longer than a lighter, but at a significantly higher cost. Lighters cost a buck or two and last for hundreds and hundreds of cigarettes. The juul vaporizer is also just as easy to misplace/lose as a lighter. As a former CA teen, lighters were absolutely trivial to get—and far less hassle than getting a juul vaporizer. Hell, you can find matches pretty damn easily, too.
Edit: Assuming the average teenager has limited funds, a lighter and pack of cigarettes is far cheaper than a juul vaporizer and pack of pods. Even once you have the juul, the pods are still more expensive than buying a new lighter and cigarettes in many areas.