because its a social and relaxing thing to do. sometimes its fun just to get drunk and meet new people who are also drunk. the things you talk about are rediculous and when you remember in the morning, or you are reminded -as the case may be- its good for a chuckle and a shrug.
if you are talking about drinking to black out, i have no idea.
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...life is good...
...mai ho oni i ka wai lana malie...