One page WordPress themes are more used in the form of landing pages as compared to fully fledged websites. These landing pages are used for certain promotions or other below the line marketing techniques which are valid for a particular period only. These themes can also be used for lead generation as well, which contains a form for users to fill in their details.
There are plenty of such one page WordPress themes which can be referred by users online and can be downloaded free of cost. These web pages are mostly standalone and are valid for only a particular period of time or for any particular campaign only.