jinxed - 9:37 pm on Jun 6, 2012 (gmt 0)
How would they know?
Because users maybe viewing a gallery page with the intention of buying the product, when instead they are seeing an image of it. Users may then be hitting the back button, returning to the SERPS and then viewing another page until they get what the want.
So essentially, they may be classifying the terms as transactional instead of informational and thus sending you less traffic.