Why do you need to government to require that? How about you only rent from land lords that disallow tenants from renting out their apartment. Maybe some people don't mind this and would like to have that as an option.
For instance it gives property owners in a residential neighborhood an assurance that a neighboring building can't decide to convert their rooftop to a nightclub potentially disturbing the neighboring buildings with noise, foot-traffic, car traffic, drunks, trash, fights, etc. If you gave individual landlords the right to make these decisions without wider oversight, you'd run into a lot more issues like these. Sure - today they can petition to override existing zoning regulations and that sometimes happens, but residential issues are larger than just an individual apartment or building.
Maybe it's just that I get peeved when people get all "landed gentry" and start thinking that somehow because they are privileged to have been able to buy a piece of property that they have a moral right to control the lives of their neighbors.
That said, I support regulations "within reason" and I suppose it all comes down to a quantitative difference in where we draw that line.
You can make an argument about not restricting the free market, but shelter is such a basic human need that I think it merits a healthy amount of regulation.