is a view controller necessary?

this HeadsUpUi sample code from apple here
https://developer.apple.com/iPhone/library/samplecode/HeadsUpUI/listing11.html

uses a view controller and a view
i was looking at the code but is the view controller really needed?
if i'm in a situation where i'm using OpenGLES on a subview of the window and want to bring in another view on top of that (after pausing all the openGLES stuff obviously) is there any point?
it seems like all the code that is in the view controller can be transported over to the subview without any problems

is there a design consideration that i'm missing?