Who is an adult in a "democratic" world...

Most people would say that a person becomes an adult at the moment they become responsible for their own decisions and actions. Their parents are no longer liable - it is the person who bears all consequences. I agree with this definition. However, it seems that in democratic countries that is not the case. I will use the example of the USA because it is the best known democracy and also because I happen to be personally effected by the laws of this country. One of the most blatantly ridiculous laws I have spotted on this matter is the drinking age law (a very frustrating law I might add - to a person who in Europe has long been considered an adult). Apparently when it comes to drinking in the USA everyone becomes an adult at age 21. This, however, makes no sense. Isn't the voting age 18? This means that a person is allowed responsibility of ruling over other people before he/she is given the right to rule their own body! I think people should be appalled at this clear lack of logic. Either the drinking age should be lowered or the voting age raised. Also - what about the age of consent? Or the age legal marriage can be performed at? Why are all these different? Once an adult is an adult he should be able to do as he wishes with his own time, money, body, or everything and anything that is in his possession. I understand that in different countries, societies, or cultures, this age could be different (or it doesn't have to be a particular age - in some societies a person became an adult once they proved their worth through some trial). What all this really proves is that none of us are adults, whether out age is 1 or 101. Our responsibilities and rights are all purely subjective and can change at any given moment. Democracy can just take them away from us all or from a certain group. In these cases age groups are being discriminated against. As I said many times before on this blog - eliminate state-organized discrimination and there will be no discrimination left in the world at all!