Negative hook angle provides an opportunity to better control your work, as the blade is much less likely to try and pull the wood through the saw or the saw blade through the wood (depending if you are talking about a table saw or a radial arm saw).
Also good for making miter cuts on architectural moldings, cutting plywood panels, or cutting non-wood materials, such as plastics as well as metal. Angles between -2° and -10° are recommended for plywood, MDF, OSB, laminate, melamine boards, and particleboards.