Is age equal to society

So in class the other day we were talking about how in our society you have to be of a certain age in order to do certain things. For instance you have to be 16 to drive a car 18 to vote, buy cigarettes, go into a bar, ect and you have to be 21 to drink. I just think that our society is rediculas in this aspect. At 18 you are a legal adult. You can go off to war, you can live on your own but you can't have an alcholic drink. In Germany you are allowed to buy alcohol at age 16. I feel like if we changed our rules people wouldn't get in as much trouble. For instance if we changed the drinking age to 18 people would not get into as much trouble because they have access to what they want at an appropriate age. 18 is the age you are a legal adult not 21. Since the drinking age is 21 more and more teens are illegally drinking. Point being they are doing anything they can to get their hands on alcohol. By the time they are 21 they will be so happy that they can finally access alcohol legally that they will abuse their privileges and drink uncontrolably. This could result in severe consequences or even death. This is why I believe that we should be able to drink at 18,because by the time we are 21 we would already have experienced what alcohol is and what it can do to you.