Chances are the new tenant couldn't pass muster, so the landlord would have a vacancy without notice and the job of dealing with abandoned personal property. So much for it being none of our business what the tenant does as long as the rent gets paid. Everything that affects our ability to do business is our concern. It is good business to be ever vigilant about the type of people who move into our rental properties. The financial and psychological benefits of keeping illegal activity and bad guys out of our rentals are enormous.
Good tenants hate bad tenants.
Good tenants pay the rent, have jobs, are good neighbors and law-abiding. They move out when bad tenants move in. They stay longer when they perceive that we're intent on keeping our properties great places to live. Lower maintenance and repair costs . Increased property values.