Why do hardheaded(troublesome) teens lie so much to their parents about hugh issues?

For example: having , drugs, gettin drunk at parties,- does you parents not care about this? Seriously you need to psychological help if you are going to lie to your parents about big things like this? Its better to tell the truth now than to punk out when they eventually find out. FYI: never did the huge stuff- , drugs, and drinking. OF course i have lied over small stuff- like an homework ignment.