Two Primary Reasons Why Growth Is Required In Your Retirement Plan...

1. Loss of Purchasing Power.

 
An individual living on a fixed income over the 20 years from the end of 1989 to the end of 2009 would have suffered a -40% loss of purchasing power over the 2 decades using the CPI as a gauge of his/her inflation (source: Department of Labor).
    

2. Life Expectancy. 

A husband and wife both aged 62 have a 47% chance of at least 1 of them living to age 90 or older (source: Government Accountability Office).