The need of absolute high resolution?

It is a difficult question and possible many people swear by different answers.  This one for example, shot with Canon 1Ds III + EF Macro 100/2.8L IS.  Although Canon 1Ds III is among the smallest camera I use for studio work, at 21 mpx it is among the highest resolution camera available for full frame 135mm DSLR. But this image, was in fact cropped at apporx. 1/4 of the original image - which in reality is only approx. 5 million pixels.
Should I take the exact image using my Phase One P65+, at 60 mpx original capture, even cropped at only 1/4 of original image, I will still get 15 million pixels.  But it is not the only reason to use higher resolution capture with medium format digital backs just to get flexibility of cropping the image - which I seldom do.  But a higher resolution picture does able allow flexible cropping with less fear of image print size becomes too small.
But can the photographer decided the framing of image during the shoot so there is no cropping needed?  Yes and no.  Yes for obvious reason that precise framing is the basic of photographer, I beleive too!  But sometimes I do crop the image; to get the right ratio of image, less often on that I crop the image to be tighter - especially when shooting packshots. But in general, I shot very tight composition.  But commercially, when one photographer shoot for a commercial assignments, he might not have control over the final image that the client or art director may want to apply thier own creative crop that higher resolution image will be beneficial. And for that, higher resultion the better!
Perhaps as a photographer can care less about the absolute resolution, in stead, focus on getting the best image, because the awful truth is higher resolution may in deed just better and more useful, although you may not need it everytime, but when it is there when you need it, you will appreciate it.