There is a good reason, though, and it's in keeping with the 'nth-of-type' selector logic: there is a selector that works the way you think, called nth-last-of-type[0]
[0] http://www.w3schools.com/cssref/sel_nth-last-of-type.asp
[sample page I made just for you on my github.io page] http://flanneljesus.github.io/