Some traders use CFDs to hedge their other investments, such as shares that they may currently hold. They may trade CFDs to go short on markets as a way to hedge short-term volatility by taking a position in the opposite direction of their share position.
If the market does fall in value, the loss to their share position could be offset by gains in their short CFD share trade. However, if the share price had increased instead, then they could close their CFD position and any losses could be offset by profits to their shareholding.