Taylor's going at an even faster rate than Lindsay. If I recall correctly, at 16, Lindsay was a high school cheerleader. Possibly filming Freaky Friday. Not going on tour (tours = alcohol + illegal substances. Any band will tell you that), partying and flashing her panties at the camera. Taylor is not even 16, she's 15. Both appear to have mothers who enable them.
On the other hand, Hayden Panettiere was pole dancing and smoking with Paris Hilton when she was 16 and has a similar family situation and she turned out pretty respectful. Kinda.
Anyway, I think part of Taylor's behaviour and style is due to her belief in this rebel image. She thinks she's a rebel. She's anti-Disney, sings her own songs (you can't put words in her mouth), doesn't have a stylist (you can't make her wear what she doesn't want to), is a "rockstar" instead of a popstar, dresses in a way that is inappropriate for a 15 year old... She smokes, drinks, wears "hooker boots", leather jackets, fishnets... all the stuff that is associated the rebel image. It's cool to be a rebel, at least in the mind of a teenager. No one wants to be the goody-two shoes Disney star.