StatsKit is a small helper for those who often start new projects and want to include all their favourite tools in one line. That’s it 
When you are learning Julia right now, I would recommend not using StatsKit, and instead, to learn the packages you need one-by-one. In this way you know where which function is coming from.
It might well be that DataFrames and Distributions is all you need for your project. Then there is no need to bloat it up by including more packages than necessary.
Reexport makes it possible that the line using StatsKits is kind of equivalent to using Bootstrap CategoricalArrays Clustering ...