Hacking, or slanted, front pockets on a jacket are typical of country suits. The angle allowed a horse rider to access the pockets more easily but also kept the items inside the pocket more secure. As they are indicative of a non-city suit, they tend to add a slightly casual aesthetic to the jacket.
Nowadays, hacking pockets are added to jackets more so because they appeal to the client looking for a customized look. Rarely are we riding horses whilst wearing a sport coat or suit, so the addition of the angle was more for looks rather than use.
The above suit was made for a restaurant employee, who accesses the pocket very frequently. Designing the suit for ease of use whilst still looking good was important for the restaurant and the hacking pockets were the only "curveball" to the exterior of the suit.
Slanted pockets tend to do two contrasting things to the silhouette of the wearer. They can accentuate wide hips as a negative (unless the wearer also had overly wide shoulders, in which case it can help balance out the garment). Conversely, they can direct the eye towards the middle of the abdomen and make the wearer look taller and slimmer.
Either way, it is an option worth exploring for most clients looking for either a functional or aesthetic feature to their suit or sport coat.