Many firms think winning the business of DIY investors is more trouble than it's worth. These investors are often thought of as potentially difficult clients, ones who require advisors to do more work and more hand-holding to demonstrate their value.
It is true that DIY investors tend to expect more from RIAs to justify the cost of working with an advisor, but there are ways your firm can demonstrate value to DIYers. This article from ThinkAdvisor explains how.