A lot of things can cause this, sometimes even people who take care of their teeth can end up like this. Of course neglect has a big impact on it. 2L of pop a day is fking dumb health wise, especially considering she never regularly brushed her teeth removing that layer of acid. From the look of this some of the teeth were not proper from birth, fking genetics (big ass tooth). The main question is, why did the person not get them treated / pulled before it got so bad? "The woman referenced in this article did not receive dental health services for more than 20 years." Poor gums. Neglectful people being neglectful.
As for comparison for drugs, it is fking stupid. Wopdie-do pop and drugs both contain acid, so does *shock* most salad dressings (vinegar), etc. Why not compare it to neglectful people who eat a crap-load of salad with a crap-load of acid-y salad dressing. In the end it is just another story that you should brush your teeth after covering it in stuff like acid, even stuff like sugars that remain in your mouth will eventually get broken down into acid and just sit there in your mouth while you sleep, slowly chipping away at your teeth. Oh and don't fking drink so much pop, called moderation.