Scatting may be desirable because it does not "taint the music with the impurity of denotation". Instead of conveying linguistic content and pointing to something outside itself, scat music—like instrumental music—is self-referential and "d[oes] what it mean[s]". Through this wordlessness, commentators have written, scat singing can describe matters beyond words... releasing emotions "so deep, so real" that they are unspeakable; his words "bypass our ears and our brains and go directly for our hearts and souls".
http://en.wikipedia.org/wiki/Scat_singing