flatbush27:
I agree about the age (they used that argument for voting age), but the law has consequences that may not be avoidable.
Imagine (CV) a child gets into an accident due to Purim drinking (DUI or not). The insurance company which pays for the hospital, rehab etc. will want rembursment from the (legally) guilty party who provided the booze. THEY will notify the police. If the family/injured parties do(es) not cooperate, the insurance company will not be responible to pay and they will be left with hundreds of thousands (if not more) in bills which will force them to cooperate.
As far as the second point, you can’t (for most people, you may be different) get the same geshmak from drinking during the seudah if you’re hung over from the previous night.
As far as Raba & Rav Zeira, is offen a Gemorah. If you don’t think its possible for a Purim drunk to die and/or kill someone else (DUI), you are living in a dreamworld (I don’t think you are, so could you please elaborate?)