Shoulder exercises are incredible for getting a rounded and sculpted delts.
Strong shoulders are very important for supporting arm and chest movements. So if you are finding it difficult to make pectoral gains, then you may need to increase the strength of you shoulders first.
Moderately exercising your shoulders, also reduces the likelihood of shoulder pain, which is commonly caused by tendon soreness in the rotator cuff due to vigorous throwing, lifting, sport or any action that requires you to raise your arms.
The shoulders are complemented or opposed by the chest, arms and back depending on what arm movement is occurring. This is a good thing, because it means that almost any chest, arm or back exercise will also in tandem work your shoulders, leading to a faster workout.
However, if you really want to focus on strengthening your shoulders, you should consider doing specific exercises for it, which in turn will also work other parts of your body.