We at the top of the food chain are charged with the responsibility of keeping balance amongst all creatures. Sharks, along with other creatures, are hunted for what their bodies can reap for the hunters. Thus will be hunted into extinction for monetary value.
Shark finning is a despicable act. Sharks cannot swim without their fins, meaning even if they are released after capture they drown shortly afterwards due to lack of water flowing over their gills. Apex predators are the most sparsely numbered in a food chain and if you remove them completely the system cannot operate in balance. The ocean is home to the largest majority of living organisms on the planet and is also one of the greatest carbon sinks at our disposal. We must do everything we can to maintain these extremely complex and delicate natural systems.