The person who owns the land makes it available by deciding to rent to people. The person who owns the land can decide to tear it down or not rent to people.
>take no risks
Real estate is not a risk free investment. It would be much more popular than bonds (when interest rates aren't near zero) if it was.
>provide no service
Maintaining the property in a habitable condition is a service. Maintenance expenses are why a large number of people choose to rent instead of buy when staying somewhere short term.
>add no value
Making housing available in desirable locations for less than the cost of a SFH is adding value. It can reduce people's commute or put them in neighborhoods they want to live in. If that land was instead covered in SFHs (which seems to be the implied ideal for the "landlords should not exist" crowd) the number of people who could live there would be significantly reduced.
>employ nobody
Landscapers, plumbers, electricians, roofers, property managers, cleaners, inspectors. In the case of new construction, a lot more people.
>often literally do nothing
Ha. I wish.