Housing is a necessity, and while, in our current system, we allow the free market to provide that, it runs counter to the goals of a stable and healthy society to allow landlords to force people out of their homes arbitrarily.
Like health care and education, there are significant long-term and short-term benefits to treating housing as more than just another contractual transaction (for example, tenants who develop a sense of ownership of their place and treat it with respect and take care of it, vs. 'who cares we'll be out in a year anyway'), or building a sense of community in an area (a psychological necessity, and one which has tangible benefits like reduced crime, which in turn improves property values).