Life is Bitter
The Fine Art of Mixing Drinks, David Embury's classic, is notable for being somewhat rigid in its definition of a cocktail. He basically divides all of cocktail-dom into two camps: the aromatic ones (Manhattans, Martinis, Old-Fashioneds), and the sour ones (basically anything with lemon or lime juice in it, though never enough to overpower the main liquor).
For Embury, a cocktail is consumed before dinner, stimulates the appetite, and isn't very sweet - or it isn't a cocktail. As such, though mixed drinks like the Brandy Alexander and its cousins do show up on the pages of his book, they are (justifiably, though somewhat condescendingly) classified as desserts when made the traditional way (equal parts brandy, cream and creme de cacao) or grudgingly allowed to stand alongside the real cocktails when made according to his modifications (basically upping the brandy by four times the usual amount relative to the other ingredients) - though with a loud admonition that the result is vastly inferior to his tried and true favourites.