DCA is not unreasonable advice given that most people's greatest enemy is themselves. DCA helps avoid the very emotionally upsetting feeling of you throwing money into a fund and it dropping 5% the next day. This emotional volatility can push people to make bad decisions (pull all their money out, try to time the market, stop investing, etc.). Scheduling your investment into smaller sums lets you diffuse the highs and lows in order to keep you steadfast.