This is a direct quote from the NCAA Manual:

"The RPI is intended to be used as one of many valuable resources provided to the committee in the selection, seeding and bracketing process. It never should be considered anything but an additional evaluation tool. No computer program that is based on pure numbers can take into account subjective concepts (e.g., how well a team is playing down the stretch, what the loss or return of a top player means to a team or how emotional a specific conference game may be)."