Perspective control lenses are great for.
wide angel interiors where you cant have any distortion (converging lines)
mid focal PC for flat copy work they are indispensable
With many things like macro for instance you can place your field of sharp focus precisely to maximize what you get at a given aperture.
there are more I am sure but these are what I use them for, I see large format cameras in use for these reasons even when absolute resolution isnt needed.
what is the purpose of PC lens? what is it used for?