A funny thing happened on the way to the robo-adviser revolution. Robo advisers--automated investment services that assess risk tolerance and manage a portfolio of exchange-traded funds at a low cost--are running into the realities of the highly competitive wealth-management market, including thin profit margins. So they are expanding in areas that didn't used to be associated with robo advisers, including managing "529" college-savings plans, administering 401(k) retirement accounts and adding account features that involve partnerships or co-branding deals. In effect, as traditional brokerage firms challenge the robos with their own lost-cost offerings, the robos are evolving. For individual investors, this evolution is blurring the line between the robo advisers and the more traditional investment firms such as Vanguard Group, Charles Schwab Corp. SCHW -0.74 % and Fidelity Investments, which are quickly adding automated services.