Most target date funds are invested up to 80-90% in equities early in their life, with the remainder being bonds and short term (cash) investments. The re-allocation to bonds as the target date is approached (at which point the fund converts to a terminal income fund) is to reduce equity volatility and sequence of return risk (ie maximize growth exposure when it can be tolerated, reduce exposure as risk tolerance declines due to approaching income need).

We'd all like to capture maximum risk adjusted returns, but compromises must be made depending on your desired outcome and constraints.