Esther has insights, Specialists AND Generalists, on Why Projects Don't Need Specialists. Her point, that people tend to coalesce around their interests, and that as specialists, they may not share interests, is something I have also seen on projects. As Esther says,
Reducing categories (having “developers” rather than many named specialists) reduces differences and helps people focus on shared goals.
Shared goals that lead to working product is the point of the project.
P.S. I realized late that I had forgotten to title this post. Fixed.