Lighters are inexpensive, common, and last a long time.
Juul pods are age-restricted consumables, just like cigarettes.
I think the lack of odor, more agreeable flavors, and less health or social stigma are more important. I doubt e-cigarettes differ much from cigarettes in how easy it is to get ahold of when underage, although perhaps adults are more willing to sell them to or buy them for teenagers on the belief that they're harmless.
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.
I'm not going to argue that it was major obstacle. Not at all. In fact I'm willing to concede that it is so much a non issue that I should not have included it on my list of reasons.
But there was definitely a year of my life less than six years ago when I was not able to purchase a lighter from any gas station in the bay area, and I'm absolutely certain that it has only gotten more difficult for teenagers since cigarettes now require you to be 21 to purchase.
And I should mention there is no law preventing the sale of lighters. People will just flat out refuse if you don't have an ID.
I had an experience as a teenager as well and "must produce fire" wasn't a meaningful obstacle. Of course your mileage may vary but lighters (and if not that, then matches certainly) were and are commonly found in households, ready to go missing.
And they last such a long time that frequency of replacement just does not matter compared to the cost and frequency of either cigarettes or vaping consumables.
Juul pods are age-restricted consumables, just like cigarettes.
I think the lack of odor, more agreeable flavors, and less health or social stigma are more important. I doubt e-cigarettes differ much from cigarettes in how easy it is to get ahold of when underage, although perhaps adults are more willing to sell them to or buy them for teenagers on the belief that they're harmless.