Much of what is important about employee feedback applies to peer feedback - it fuels growth, development, motivation and direction.
A drive specific to giving peer feedback is relationship or team-building. Building communication and skill-sharing between your employees not only promotes a trusting and inclusive environment but diversifies the skills of your team.
The best teams are diverse, consisting of different people from different backgrounds and varied assets. The most successful teams do not strive to be the same but rather, initiate in a mutually-beneficial exchange; a trading of skills which enables employees to maximise their strengths whilst building on their weaknesses.
Establishing a climate of frequent peer feedback also serves to reduce conflict in the workplace - a small silent problem can quickly grow into a nuisance and even a few of those in a team fosters a big problem for morale!