I mean honestly how many adults just decide "Im going to start smoking cigs". If I had to bet, I would say 80% of all smokers began smoking when they teenagers. Teens are still developing and cannot make proper "adult" decisions. Big tobacco whether they want to admit it or not knows they must go after teens because if they don't trying to convince a 35 year old with three kids to start doing something that they have never done is damn near impossible...

Its the same strategy that some companies use where they work with the earliest stage companies, i.e. Stripe, and they grow with them. In an extremely perverted view, big tobacco just wants to grow with their customers hahaha.