slmd, yes, less tissue to maintenance. That's the main reason. You're a smaller you. That's why, as your near your ultimate goal, you have to actually recalibrate. There comes a time when the old calibration doesn't amount to a calorie deficit.
Another factor to consider is non-exercise related activity. Typically, as people near their weight-loss goals ... it falls off. This is why some people wear a pedometer, to ensure they're getting their general activity (which is where you burn most of your calories through movement).