University of Bath Portrait Paintings

Why so formal?

I really love these portrait paintings. After working at the University for nearly 3 years as a photographer I have seen first hand the formal style of images they require and have even written into a document for freelance photographers describing portrait poses and depth of field etc. These paintings have almost exactly the same formality to them as many of the photographs taken of the Vice Chancellors at the university... Just caught my eye and found it quite interesting. 

What creates a formal style of image making?