Covered calls are a neutral strategy used by investors who feel the stock price won’t dramatically fluctuate for the duration of the call option. Typically this strategy is used by investors who intend to hold their stocks over the long run. However, a long term investor may want to make money in the short term. Essentially a covered call acts as a short-term hedge on your long-term stock position.
Because they feel the stock won't dramatically go up in price in the short term, they simply write a call option to make money from the option premium.