Balanced or Not

I own a preamp which has both balanced and single ended jacks. I assumed that since I was using the balanced jacks I was getting the benefit of a balanced circuit. I have just now realized that just having balanced plug-ins doesn't mean your preamp (or any other component) is "balanced." Just wondering what sonic compromises are being made with equipment which has balanced inputs and outputs but that change the signal to single ended as it passes through it. If you are using the balanced outputs, what good is that if the signal going into this jack is single ended? Why would manufacturers do this? What is the advantage to not following the balanced circuit through completely?