Mainly because that sort of thing will always come back to bite you in the ass.
When I worked at the public library, I often checked out books to parents about "1,2,3 discipline" and "spirited" or "indigo" children. What I used to think was, well, I don't know that you've got 'spirited' children--you might just have brats.
And here are the titles I checked out at the library the other day: Difficult to Delightful in Just 30 Days; Taming the Spirited Child; and Raising Your Spirited Child.*
*Please note that neither of the CRjrs are really too "spirited." I'm just busily trying to find some nice, harmonious way to reconcile my massive need to control with their massive needs to not be controlled. We're all learning here.