Cultural kin selection represents an alternative perspective which makes little mention of selection acting on groups. Instead of humans being part of innumerable overlapping groups, their genes and memes are modeled as being related to the genes and memes of others. This perspective has been much more enlightening in the organic realm, and I think it will prove to be much more enlightening in the cultural realm as well. The largely-fictional groups of group selection are just a clumsy and awkward way of viewing the situation - most of the time. The perspective has a long history of producing dud science.
In most of evolutionary biology, 90% of scientists are using kin selection and 10% are using group selection. In the social sciences, it's the other way around. I think that this fairly clearly indicates the existence of a problem.
Why is group selection still so popular among social scientists? For a long time many of them held out hope that it would prove to be a new theory of social behaviour. These hopes now appear to have been crushed by the failure of the theory to make different predictions from the long-established orthodoxy of kin selection.
Social scientists have a long history of not understanding how evolutionary biology applied to their subject areas. As a result there's a large scientific lag afflicting the study of cultural evolution. Group selection enthusiasm seems to be clearly one aspect of that: the numerous social scientists involved are stuck back in the 1960s somewhere, where the virtues of the kin selection perspective were not yet widely appreciated.
Lastly, group selection in the social sciences seems to have found extensive funding from the John Templeton Foundation. In a surreal twist to the final battle between science and religion, group selection enthusiasm has been funded to the tune of millions of dollars. That kind of marketing budget can buy a considerable quantity of confusion.