This doesn't mean that you are an overbearing parent, but a caring one. Rules like no use of alcohol or any other drugs when driving, and no lifts home with drivers who have been drinking or using other drugs are important for your child's safety. No one factor causes someone to use drugs or develop a drug problem. So no-one else is responsible for someone else's drug problem. There are usually many reasons why someone starts to use a drug and many other reasons why they get into trouble with drugs.
Teenagers make their own choices, just as adults do.
Of course, your attitudes and behaviour affect your children. The family environment has a very important impact on everyone in it and all the good things that happen, as well as the bad, leave their mark. As a parent, you want your children to learn from you. Unfortunately, they learn bad habits as well as good ones. If you drink alcohol regularly, your child is likely to imitate that behaviour too.