Using a wide grip does NOT provide more stretching of the muscles involved; in fact, it literally prevents much in the way of stretching, limits the range of movement and turns a potentially very productive exercise into a very poor exercise.
– Arthur Jones
When you struggle to get stronger, it feels tempting to perform an exercise in an easier fashion. This feeds self-deception, like justifying that plate of tasty sugar and fat-laden morsels that harms your health and happiness in the long-run. Many will cut down on the range of motion and pile on the weight. Some change up the exercise in minor ways under the guise of including variety. Others will take a much wider grip or stance. You may gain leverage and therefore perform better on the surface, but do so at the cost of your joints and the true goal of strength training.
The objective is to build muscle and grow strong, NOT to lift heavier weights per say. This means you must also use good form. Good form means using a medium position which protects the joints and allows all the active muscles to work. You know you use a medium grip or stance when you achieve the most range of motion possible for an exercise. Too little range of motion will lead to poor results as you will fail to reach the midpoints for each muscle. Your muscles create the greatest tension at the middle of any normal motion, and tension is the main stimulus for more strength and size.
On the bench press, trainees that grip too widely feel a pinch deep in their shoulders. The best arm position relative to the body is 45°. Many trainees bench closer to 90°, flaring the elbows and causing shoulder impingement. You see them stretching out and contorting their arms to deal with this pain after bench pressing like a white guy pulling off his best dance moves. With a slight elbow tuck and a narrower grip, you prevent the shoulder issues and also give a fair share of the workload to the triceps instead of mostly the chest. This also applies to wide-grip pull-ups which also impinges the shoulder and avoids working the biceps enough. If you follow my philosophy of focusing on the big three, these issues matter greatly since you rely on only three movements to train the whole body.
You also lose explosiveness. It feels difficult to accelerate with an extreme stance. On the squat, many trainees take a very wide stance that leaves their hips aching. This tightness also makes it tough to get enough range of motion. They fail to rise quickly from the bottom and can get stuck there often. This also reduces the stimulus to the quadriceps. It prevents the knees from achieving enough range of motion to stimulate maximum tension in the quadriceps. So although a wide stance squat may work for some powerlifters with super elastic suits to lift more weight for their sport, it turns an excellent exercise into one that rips apart your hips and ignores the knee extensors.
Eventually you do have to use heavier weights and get more reps to improve, but never at the expense of good form. Avoid going too widely on any exercise. You may feel alright about your choice at first, but in the long-run you will suffer from painful joints and poor development. Choose a medium grip instead and analyze your training and recovery when things get tough.