Kin selection was originally discovered in the 1960s. It contributed significantly to to an enormous revolution in our understanding of evolutionary biology - the gene revolution.
The discovery of kin selection and intra-genomic conflict destroyed the idea that organisms acted as harmonious wholes. Instead, it became clear that organisms were uneasy alliances between factions with overlapping - but different - interests.
As in the organic realm, cultural kin selection is invading territory that was previously occupied by inadequate group selection theories. Today, group selection enthusiasm still rampant in the social sciences. In the organic realm, the switch from group selection to kin selection was a large paradigm shift. Kin selection wound up almost totally eclipsing group selection. Quantitative measurements of relatedness replaced fuzzy and often-inaccurate just-so stories about how some groups reproduced faster than other ones. In the organic realm this was a large displacement of poor quality science with better ideas that were more easily subject to quantification and testing. Group selection isn't exactly wrong - but kin selection carves nature at the joints - while group selection is more like chalk scraping on a blackboard. Regarding family members as promoting each others interests due to shared genes makes a lot of sense. Viewing families as consisting of partially-overlapping groups does not - because the "groups" involved are little more than mathematical abstractions. Kin selection was so obviously superior to group selection that the latter was relegated to the gutter as a tool for understanding the evolution of cooperation.
Cultural kin selection seems likely to result in a big boost to the meme's eye view. In the organic realm, the gene's eye view was often used to help visualize how kin selection worked. Similarly, in cultural evolution, it is often helpful to descend to the level of the meme to fully understand the dynamics of how cultural kin selection works.
Cultural kin selection helps to explain social cooperation. Understanding cooperation is important - partly because conflict can be so destructive. Cultural kin selection helps to explain our economic system, copyright law, our education system and how our military forces operate. It helps to explain why humans congregate in the groups that they do. As in the organic realm, cultural kin selection is tremendously important to a proper scientific understanding of the world.
Hamilton published on kin selection in 1964. Since it is 2014 at the time of writing, that was 50 years ago. This gives some indication of the scale of cultural evolution's scientific lag.