A student wrote to me for background information about the use of shark fin in Chinese cuisine, in connection with the ban in California. I replied:
The main reason for the cultural value of shark fin soup has to do with the Chinese tradition of "face", i.e., showing respect for the public prestige of one's guests. The fins themselves (called yúchì 魚翅 'fish wings') contribute a distinctive texture to soups made from them. This texture is hard to replicate from other ingredients, and it is true that Chinese cuisine places great emphasis on texture.
But texture itself is only indirectly the cause of the shark fin's value. The actual reason is that since the thing is so hard to replicate and so expensive, providing it for my guests is a way of showing them "face" — showing them that I am willing to go to trouble and expense for them. The intrinsic qualities of the food are much less important than the fact that the expense and distinctiveness of those qualities make it a good token for showing respect.
Making shark fin illegal would certainly increase the "face" value of the food still further. I have been served several endangered species at official or semi-official banquets in China. They were not particularly tasty — pangolin, in particular, I found quite vile — but by serving them to me and my sponsors, the host was showing respect.
This is a central element of Chinese culture, and if you think about it, not totally unrelated to ideas you can observe in American society. The next time you are in a fancy Western restaurant, look for items that are more expensive than their intrinsic character would warrant. Ever see chocolate cake with gold leaf on it? Exactly how much flavor do you think gold leaf has?
If you want a better analogy with regard to environmental impact, consider this.
If you talk to businesspeople in the US, you'll hear some of them say that regulation of industry and substances is futile because it increases the motivation to break the law, increasing the cost of regulation in a spiral because of the continual need for further enforcement. Making a substance illegal raises its price and gives dealers both the reason and the resources to break the law, bribe law enforcement, and defend their businesses with violence. Placing tariffs on an import increases the motivation to smuggle it, to misreport sales and import figures, and to bribe customs agents. Etc. You will find many people in this country who say they believe in this principle.
Similarly, the more severe the consequences of supporting trade in endangered animals, the higher the value of serving it to an honored guest in China.
If you believe, as many Chinese people do, that institutions are intrinsically corrupt and personal relationships are the most important thing, then you can see why these foods continue to be served.