Why is the image quality on ITV1 HD so dire, especially with sports?

I was watching Aston Villa vs West Ham on there this evening and it might have been the worst HD picture quality I have ever seen. It was like watching an internet stream that never improves in quality to the point that even YouTube highlights look better.

Says a whole lot that even Now TV looks cleaner to watch. How is it even deemed acceptable for a national broadcaster to be that bad?