Why the obsession with file sizes and lots of pixels?

I've often said that size matters in terms of stock photography. Its why I often buy and use cameras that aren't neccessarily what I would choose if I didn't make my living in this way. In a previous post I wrote about the D800E and how downsizing the files makes them look sharper. The above graphic, which shows how the stock photography websites I place my pictures with sell them, demonstrates the advantage that high pixel count images can have. 

The above is an example of a D800E file. The XXXLarge size is the full size file. However by far the great majority of file sizes that I sell are in the Small to XLarge catergories. This means that these downsized images will look very sharp, in most cases sharper than a file shot on a camera that has a similar size but smaller native resolution. 

This works for me in two ways, firstly clients interested in buying my pictures will assume that because the file they are purchasing is shot from a larger original, the chances are it will be high quality. Secondly when they actually download the file that impression is confirmed. 

So its not just the possibility to crop a large image that gives it an advantage, it is how it makes the smaller images that are derived from it, look much more impressive. Since  picture buyers on most stock photography websites have to make a decision as to whether to purchase based on a thumbnail, this perception and experience that large high pixel count files yield better quality images at smaller reproduction sizes, helps. It is also to my advantage that these downsized images from a camera such as the D800E look so good. It is obviously the image that counts, but if a buyer is considering two similar images and they have used one of mine before, they might be more inclined to select mine because I provided them with pictures that exhibit good sharpness and high resolution in the past. 

Just thought I'd write this to show that "pixel-peeping" does indeed have its advantages.