The ScrumMaster is one of the most undervalued roles in Scrum and Agile. Most teams that are just starting out don’t see the value of having a full-time ScrumMaster, and they try to combine this position with that of a developer or tester so that the ScrumMaster is “working.” It’s one of the most common misunderstandings of the ScrumMaster’s role, and the majority of novice groups struggle with it.
Source: “The Great ScrumMaster: #ScrumMasterWay“, Zuzana Sochova, Addison-Wesley Professional