Who uses derivatives ?

Institutional clients

1. Banks act as Market Makers (they act as dealers who provide binding buy and sell prices to the market)
2. Other institutional clients Funds etc. often sell Calls on parts of their portfolios (if they want to lock in some profits). Furthermore, they use futures and options for risk management purposes.

Retail investors

Retail investors often use derivatives to leverage (possible) profits. Or they use them to hedge their assets against market downturns.