Time Availability – Outside regular job hours there is less time available for individuals to put across for investment and understanding the same inside-out.
Self Interest – Sometimes due to lack of interest folks are not able to focus on "Financial Aspect". In order to DIY everyone needs to have the focus to read & practice various investment strategies for respective personality. This comes through high degree of financial knowledge & they putting the knowledge to work.
Lack of Confidence to take the plunge – Even after going through understanding of the financial markets, >90% of the folks are not able to gather courage to go ahead and invest. Mostly people believe in going for professional advice which is by design created to being average. Thus most of results in average returns due to management fees, as fees & performance are not tied together.