As a whole, Flexibility ("Glossary") is usually the forgotten component of fitness. Most people will skip this type of exercise (involving some type of stretching) because they do not really see the benefits like they can with Cardiorespiratory exercise or Weight training.
But flexibility can do your body a wealth of good. Some of the major benefits of engaging in some type of a stretching routine include:
Reduces stress in the exercising muscles and releases tension developed during the workout.
Reduces muscle soreness if you stretch after you workout.
Assists with posture by balancing the tension placed across the joint by the muscles that cross it. Proper posture minimizes stress and maximizes the strength of all joint movements.
Reduces the risk of injury during exercise and daily activities because muscles are more pliable.
Improves performance of everyday activities as well as performance in exercise and sport (most of which can come from a more flexible hamstring muscle... which can improve speed).
Slows joint deterioration as a person ages.
And a huge benefit, reduces back pain... about 85% of Americans will experience back pain during their lives. One of the largest causes of back pain is lack of flexibility in the lower back, through the Gluteal muscles, and into the Hamstring muscles.