I think it is so that we are all impressed with the freshness of the goods and therefore purchase more - it bugs me too, I don't really know what veg I want until I have done the rest of my shopping - so then I have to battle against the tide, or I forget something!
There is a very scientific reason for this that has been discussed on many TV shows. From memory, I think it is to do with the way peoples brain works with colours and smells enhancing the likelihood of spending more money. The fruit and veg areas are usually lit with different bulbs, with a more blue tinge, which make the colours of the fruit and veg look more vibrant.
i thought it was that the smaller items are at the front of the store a larger near the end cos if u put large stuff in ur trolly first u would buy less as u would feel u did not have enough room in the trolly for other food but by puttin everything else in first u make room for the large stuff.
does that sound stupid, starting to think i made that up lol