Because T Rowe offers a wide variety of no-load, but actively managed funds with good customer service. There's nothing wrong with index funds, but I want to at least try to be more than average in my investments. Dodge & Cox, for example, has only four funds -- good ones, but still only four (a fifth may come soon). But T Rowe has a full selection of funds for every need. (No, I don't work for T Rowe, or for any fund company.)