Shooting double action offers several benefits. First and foremost, if one carries a revolver, chances are it will be used in double action if it is ever needed. The ability to get consistent hits with the long heavy trigger pull is important. Secondly, if a shooter can learn to shoot accurately with a double action revolver, then they can shoot almost any handgun accurately.
I never got shooting a DA revolver in single action mode, I mean – you paid extra for double action, you should use it!