One of the purposes of making money laundering a crime is that it makes it possible to investigate other crimes. You know the mob is making money and you know they're moving that money around somehow. Making money laundering a crime gives investigators a place to start their investigations. If they think a laundromat is a front for the mob, they can prove that by counting how many people are using it and comparing that to how much money they're putting in the bank at the end of the month. They can then get a warrant to investigate further. A judge shouldn't issue a warrant on a laundromat for investigating a murder when there's no clear thread that connects the two. A judge could however issue a warrant to investigate money laundering when you know the laundromat's books don't add up.