Landlords and scalpers seem very much not equivalent. I would compare scalpers to property flippers. Someone who sees an asset for sale for less than its market value and purchases it with the intent to sell it very soon after.

Landlords provide flexibility to the market. They take on the risks of owning. In a fully healthy system, it would still be very good to have landlords and rental properties, people would just pick them because they are the best option, rather than the only option.