In a word, convenience.
This is the same reason that I recommend programs such as or --they dispense with all the graphical-design baggage packed into a full-featured image editor like Adobe Photoshop, and include only the stuff that's important to photographers editing photos. In the same way, a RAW editor is a photo editor stripped to the bone, sporting just the features you need to correct color and exposure. A lot of the time, you could make a few tweaks in the RAW editor and be done, never needing to mess with the bigger Photoshop, Photoshop Elements, or PaintShop Pro.
Accessing Adobe's Camera Raw is pretty simple: It pops up automatically whenever you try to open a RAW-format photo in Adobe Photoshop or Photoshop Elements. In fact, you might know Camera Raw as "that program you must click OK on in order to get a RAW photo into Photoshop."