Necromancers and clerics of the death gods are at best seen as necessary evils, and at worst abominations. Dread necromancers tend to fall into the latter group; when discovered, they are often hunted down and killed. A few enclaves of theme exist, in far reaches of the world or in lands where the living fear to tread, but for the most part they are quite rare.
The same races that become wizard tend to become dread necromancers, such as elves and gnomes. Humans rarely have the opportunity to discover the knowledge of necromancy, but those that do are often the most formidable of them. A few orcs and half orcs become dread necromancers, as their culture supports the pursuit of power. Among other races, githyanki commonly become dread necromancers, while a few other races have it as a common class.