I hadn't noticed that. Then again, notice how in other contexts a seemingly smaller difference is noteworthy. If our unemployment rate rises or drops by even 0.1%, all the news agencies are reporting it, as that still represents a lot of people. Likewise, a local TV news program noted that my local area has a somewhat smaller percentage of males than the national average (I think about 0.2% less) and asked, "Where are the men?" Again, I guess 0.2% still represents a lot of people, though it seems on the face to be a slight difference.
It would be interesting to see the data on happy vs. less happy states charted as a bell curve, and then statistical analysis to determine actual significance of the scores. An eight point spread may or may not be significant. Also, the criteria selected to denote "happiness" might not accurately measure or predict that vague and elusive condition. For example, making unhealthy lifestyle choices was considered indicative of reduced happiness. But who is to say that a person who smokes or eats fatty foods is less happy than someone who does not? I think you can have been habits and enjoy them. I have!