I used to be a programmer who transitioned into BA/PM role lately. I see and understand the pains of both sides. Sometimes, I want to switch into the technical/programmer mode where I want to solve/code the thing myself. The point is that these 3 roles even though not necessarily mutually exclusive, are very difficult to do at the same time especially in large corporate environments. At a startup, I am not sure if do need a separate BA/PM but when you have to deal with 100s of business users across multiple countries, get everyone to agree on scope/requirements, keep effective communication with all stakeholders etc. etc., you need people who can do all these. This is where a good BA/PM comes in. The value of a good BA/PM can never be undermined even though it can be argued that a developer usually fills these roles many times in certain circumstances. To summarize, a good BA/PM is not someone who only is good at business/domain knowledge or a set of tools, but is someone who can deal with people, glue teams together and is not afraid to wear many hats which could include cold calling team members, pestering business users to confirm things etc. etc.