Most people don't realize that holding the kettlebell overhead for a period of time is actually a core workout instead of an upper body one. Oh sure, you have to stabilize the shoulder and there are carry over benefits to the upper body, but the core gets worked hard. That's because you have to stabilize the mid-section in order to hold the kettlebell up.
And there's the alignment of the bones one over the other all the way down the kinetic chain to consider. Whent he bones sit one on top of the other, you can actually take an active rest in this position. People that don't train the kettlebell can't understand this, but it's true.
For proof, look at this clip of a Russian women's competition. Notice that they rest in the overhead rack position.
Overhead rack is a potent tool in your tool box. Use it often and skip the crappy crunches.