Why alcohol should have a drinking age of 18.

 If someone is old enough to die for there country, elect the person that runs this country i dont see why they are not able to enjoy a nice cold beer. If they are seen as an adult in the eyes of the law then why can they not make the decision to drink. If 18 year olds are so responsable then why cant they handle the effects of alcohol. If  a person is able to make the horrible decison of choosing to abuse tobacco why cant a person choose to consume alcoholic bevrages?

They are said to be "irresponsable" an unable to "handle it" then who is supposed to be responable for them if they are an adult? An 18 year old is responsable for himself only. If this statement is true what is the point of pushing the drinking age back  3 meaning less years?

I find it rediculous that  a person that can be responsable of a family cannot control the effect of a beer.