This clause is not well known but it has been kept in throughout all of the changes (four I think) to the Residential Tenancies Act since 2016.
My guess is that there is legal advice to say that you have to allow for a no-grounds termination at some point during the tenancy by a landlord. There were two Supreme Court decisions in 1981 and 1982 which struck down attempts to regulate rents and the Attorney General will be mindful of having to work within these parameters. The Supreme Court found that tenancies of indefinite duration and rent controls were unconstitutional, with the implication that one or other was okay.