For a DAC to function properly it must have a stable reference to create a precise output signal. Unfortunately because it is a simple concept, proper reference design is usually overlooked. In this app note from TI a simple force and sense circuit is used to help stabilize the reference voltage.
The article points out that the current draw from the reference depends highly on the code the DAC is using to generate the output signal. This variable current creates a variable voltage drop over the resistance between the two circuits. While this voltage drop is usually negligible, in DAC design it could compromise the precision. From the DAC point of view the reference just became variable. With the help of a buffer circuit this problem could be eliminated.