From a reader:
The answer is pretty simple: “They are adults and are allowed to do what they want with their lives”. Mr Bush can’t force them to do anything. The Clintons had to make a choice to send Chelsea SOMEWHERE to school, so maybe there was a 50/50 chance it would be public or private. Enlistment in the military, at least the last time I checked, is still voluntary, and is chosen by a small fraction of our citizens. So I, in general, would not expect them to enlist just from probability alone. I just think all of the questions about them not serving are, well, pretty stupid.