I think you raise a very interesting point. When you read stories about trading, often people bring up the question, "What value does it provide to society?" Much of the commentary I read wants to apply that judgement to trading, but nowhere else. Are designer jeans a benefit to society? Is fast food? Are casinos? Does everyone's job need to be beneficial to society? And if so, who makes that call?
Clearly designer jeans and fast food are more beneficial than casinos and zero-sum trading. The first two are at least somewhat useful, are not that addictive and do not harm anyone except maybe people who eat too much fast food. Casinos are of some entertainment value, but are very addictive and have negative effects on neighboring communities. Zero-sum trading is tricky, it is not that addictive but very few people benefit from it at all, less than from casinos and much less than from designer jeans. At the same time negative externalities probably exist but are not well studied.
