Concrete driveways can sink due to a variety of reasons. The most common cause is moisture infiltration, which can be caused by a number of factors, including inadequate drainage systems and poorly sealed seams. Other causes include heavy rainfall or snowmelt, age and wear and tear, and the use of incompatible materials in the construction process. If you notice that your driveway is sinking or has started to do so in recent years, it may be time to consult a professional for help addressing the issue.