For one, I personally cannot trust the technical competence of a fellow developer if he/she cannot handle their setup him/herself. We're talking installing tools by clicking around, aren't we? The same argument holds true for a fellow plumber that has never worked with this pipe system in particular.
Second, there's much to discover by installing and setting up everything by oneself. It can give insights on how things are connected to each other tool wise which is the first step of getting familiar with a new environment in the first place anyways.