As a complement to chrisaycock's option, I would also say that shorting options is useful when you want to create option strategies. Buying and shorting options on the same underlying with different strike prices allows the investor to create products with elaborate payoff which allows them to be more on a range of the underlying's price rather than on its direction.

Well known examples are:

• Straddle
• Reverse straddle
• Butterfly
• Iron condor

As a complement to chrisaycock's answer, I would also say that shorting options is useful when you want to create option strategies. Buying and shorting options on the same underlying with different strike prices allows the investor to create products with elaborate payoff which allows them to be more on a range of the underlying's price rather than on its direction.

Well known examples are:

• Straddle
• Reverse straddle
• Butterfly
• Iron condor