Two things to note...
Firstly, Psychology and Sociology - all derided from time to time by commentators - are crunchy!
Secondly, the majority of the 'smooth' subjects (i.e. on the Not Suitable For Cambridge list) have practical elements which require significant skill; just not skills that are relevant for the range of traditional courses offered at Cambridge. For example, Media Studies, which includes film-making, Drama which includes acting, Dance and Photography... These are not 'easier' per se, they are different.
Personally, the hardest learning experience of my life was participating in a Drama workshop as an adult. Drama A-level would be a huge struggle for me. I doubt I could get one of those 'easy' A's. (I have a full measure of pre Curriculum 2000 crunchy A-levels; and I live with a Drama teacher so I know what the subject entails) The lowest exam mark I ever got was for Art, in which I was examined for the first (and last) time aged fourteen. It was an utterly humiliating experience for me - I was a straight A student up till then.
Sure, physics ain't a pushover. And we definitely need more physicists and chemists applying to university - that's a whole different issue. But as I say to students when they say 'which A-levels are easiest?' - it depends on what you find easy.
Actually, I think Cambridge have phrased it rather well.
The list below details the A level subjects that provide a less effective preparation for our courses. To be a realistic applicant, a student will normally need to be offering two traditional academic subjects
They are reflecting the fact that they offer only traditional, academic courses at a world class standard delivered in a conventional way. In order to realistically study those courses, a particular set of gifts is needed, evidenced by a particular set of results. That's not a scandal.
The scandal, as Boris has identified, is that 'we live in a mad world of league tables' and this culture has distorted schools' advice to students and the curriculum options made available.
There's nothing wrong with saying that subjects are different. But as I commented in my post on Jan Sramek, we all have subjects we find easier and subjects that present a significant challenge (in Jan's case, why did he accumulate 10 A-levels rather than stretching himself by taking fewer and including some literary or essay subjects instead?) Let's not fall into the easy labeling of 'hard' and 'easy', 'crunchy' and 'smooth' and join in the eternal denigration of some subjects.
I interviewed a young woman today for admission to a post-sixteen course who had low grades in some crunchy subjects at GCSE, but an A* in Textiles and another in Art. She is obviously very talented indeed in ways I can't imagine. I hope we can put her onto a course where she will flourish, be challenged, and be able to access the top universities or institutions in her field. Which will not be Oxford or Cambridge. But that's fine because she wants to be a fashion designer. Not a journalist and Tory politician...