Cleaning laundry is meant to remove all the dirt and germs. Most of the time the clothes are washed together with the underwear. Surprisingly underwear contains about 0.1 grams of fecal matter. Therefore, if you put your clothes and underwear together for washing, your laundry will end up with a trace of fecal matter.
This has harmful bacteria such as Ecoli and coliform. The washing machines are not left out, because they also contain traces of the harmful bacteria and fecal matter.