To get the benefit of higher pitching rates associated with dry yeast, it should be rehydrated. The dehydrating process is pretty rough on the yeast. The ones that are left alive are dried out and weak. Dumping them into sugar rich wort can cause osmotic shock. That is the sugar in wort will draw out any remaining moisture in the cells. This leaves a weak cell wall, making it harder for yeast to bud (reproduce).
Per Jamil, the yeast companies tell wineries, who use a lot of dry yeast and even pro brewers to rehydrate. Why not us? Dry yeast is roughly 20 billion cells/gram, (mrmalty.com). You get about half that viability by sprinkling dry yeast on the wort.
Also, if it comes up, making a starter with dry yeast is not necessary. Starters are useful for liquid yeast which only contain 15-18 billion cells (mrmalty.com). The starter gets the cell count up the the ~180 billion cells needed for a middle of the road ale.