I now take my own hashi to restaurants. It's never too late to start. My opinion is that the Japanese are exactly the same as most Europeans in wanting to help the environment, but don't have the opportunity or the full facts. The legal drinking age in Britain is 18. I have in my past also been a head Barman in a very busy Pub in my hometown.
Beer is far more popular than cocktails, and whisky is taken with a lump of ice and nothing else.
The law in Britain, I think, is quite clever. Therefore the law in Britain is that it is not illegal to ask for alcohol, but it is illegal for the person to sell it to an underage person. Therefore the responsibility is on the shop owner and bar staff. I would often ask for ID to prove age if I wasn't sure. Partly due to well targeted government campaigns , due to social pressure, and of course to personal common sense.