When grinding meat, it's always desirable to have everything cold. I like to have the meat partly frozen during the grind, since this results in the best quality product. If the meat is too warm, there'll be "smearing". The image on the left shows what happens when the meat it too warm during the grind:
The fat isn't integrated well, and it will separate more easily during cooking, resulting in dry meat without the flavor you expect from properly ground meat (as shown by the image on the right). Cold is the friend of meat grinding.
The reason I freeze every component that contacts the meat is to keep the meat cold. The friction created by grinding warms up the meat somewhat, but not enough to cause smearing, as long as you have a good meat grinder and frozen meat at the start. A room-temperature grinder will warm up the meat faster, so I freeze all the labeled items; the body of the grinder - which doesn't touch the meat, and which contains the drive motor - should never be frozen.
Also, when you're slicing raw meat almost paper-thin, such as for pepper steak subs, it is also best to have it partially frozen, so that it doesn't tear.