Licensing schemes can serve purposes which are indisputably genuine and valid. They can, however, also be used as money-making schemes, particularly during times when regulatory authorities are strapped for cash. Licensing schemes can, therefore, often be controversial, especially in situations when there are arguments on both sides. Landlord licensing schemes are a case in point.
The argument for landlord licensing
What we would now call rogue landlords have existed for hundreds if not thousands of years. You only need to take a look at classic literature to see fictional examples of them, which were presumably modelled on real-world people. There is no doubt that they exist today or that their ranks are supplemented by landlords who might not, technically, be rogue in the sense of deliberately bad, but unprofessional due to laziness, incompetence or general lack of interest in their tenants’ welfare.