In the Anime there's a short mention about Succubi and how they are organized. The Chief of the Succubi is also a prominent Side Character. They are also highly regarded in Demon society.
Succubi (and probably Inccubi as well) are organized and have a leader.
They are more or less regarded as Heroes for doing their work to their fullest
Due to their social standing they also have considerable leverage against their higher ups
TL:DR: Apparently Working conditions in Heck are better than anything in the real world.