If you're under eighteen, you're advised not to drink because the body is less well equipped to cope with the effects of alcohol, physically and emotionally - your liver's not fully developed (your liver breaks down the toxins in alcohol) and neither is your brain. This is why the UK Chief Medical Officers in 2009 issued guidance for under 18s suggesting that an alcohol free childhood is the best option, but that at age 15 some use in supervised situations is acceptable. See the
The most interesting contribution to this debate so far has come from James Alexander, the president of the National Union of Students in Scotland. He argues that an age change is a soft option and that the really challenging thing for ministers to do is “change people’s attitude towards alcohol, to change the culture in this country around binge-drinking”.
Is It Time To Lower The Drinking Age To 18? | HuffPost
There is a logical flaw in the Scottish proposals because the new age limit will not apply to alcohol bought in pubs, presumably on the grounds that this is a controlled environment. This suggests that the proposed curbs are aimed less at curbing binge-drinking than at keeping it off the streets.