Whether top-load or front-load, new or used, every washing machine provides an ideal habitat for mold. The high moisture content in both the machine and the resulting atmosphere, the typical poorly-ventilated laundry room with its stale warm air, and the continual supply of decomposing organic material provided by soiled laundry all contribute to an environment conducive to mold growth and its accompanying mildew smell.
Don’t wait until you experience that distinct mold odor. Because of such steady, mold-welcoming conditions, it is important to be consistent in regular maintenance. Cleaning a machine that appears to clean itself during each use might seem a little superfluous, but even washing machines could use a good wash from time to time.