Having a financial adviser enables the investor to carry a psychological call option. If the investment decision turns out well, the investor takes the credit, and if it turns out badly, the regret can be lowered by blaming the adviser.
Reality looks much more obvious in hindsight than in foresight. People who experience hindsight bias misapply current hindsight to past foresight. They perceive events that occurred to have been more predictable before the fact than was actually the case.