Mops are absorbing all the dirts and stains off the floor. This makes a good excuse for it to hold bacteria, dirts and germs that we don't want to keep it so far in our houses. On the other hand reusing the mops in this case will put the germs, bacteria and of-course the dirts back on the floors.
Sometimes an unclean mops creates a bad and mildew smell when using it which is absolutely against the feeling of a clean area. So to clean my mop I just start by soaking it into warm water with some detergent and start the process. This is my mop before cleaning.