From this Reader’s Digest article, The Importance of Strength Training:
The consensus is growing: Strong muscles are good for everyone. In fact, the American Heart Association now recommends that all adults strength train their major muscle groups at least twice a week.
The benefits mentioned in the article:
Strong muscles require active living.
More strength results in more protection for your joints and your back.
Improve your looks with strnger muscles.
Strong muscles help you lose weight
Strong muscles give you a mental boost.