LW, you know I love you, but I am disagreeing with you on this one. I drank since I was 14. We had older friends that would buy for us. My brother was 5 years older than me, and any of his friends would buy for me. Its just how teen culture works. We sat around a campfire and drank and had a good time. There is nothing else to do in a small town. The government says at 18, I can be drafted and sent to die for the political gains of politicians, yet I can't drink a beer? Fuck that! I knew that was bullshit, and so did all of my friends.
Its an unwritten law that if someone trust you enough to buy you beer, you should be responsible enough to own up to the consequences if you get caught. His sister bought him beer out of love and trust. Now I'm not busting is balls anymore, he really does seem to be destroyed about this.
Buying beer for a younger friend or relative is really an act of kindness. They know they they are taking a huge risk, but they do it anyway out of love or admiration.
LW, I think the reason you are so against it is you have 2 young kids that you do not want people buying beer for, because you are in that motherly protective state of mind right now. Just try to think back before you had kids. Its different when they aren't your own kids because I think the protective neural circuitry isn't really activated until you see your own flash and blood for the first time.