In a nutshell, its because my html, css, and "[blogger]" coding skills are lame.
Here's a background post I wrote when I was in the midst of the frustration of trying to make this work.. But basically, as much as I try, I can't get the "Item Page" title to link back properly. I had what I thought was the code, but the [$BlogItemURL$] is returning the url with the letter a after it, and thus "blogger cannot find the page you're looking for." and it's particularly ugly on the Item Page.I spent four hours on the dang thing before I finally decided just to put a link on it, and then have another link to this fashionably pithy excuse. If I was doing this for either $$$ or somebody else, I would obsess on it until I could make it happen.
Anybody who wants to look at my code, and tell me what I'm doing wrong is totally welcome. Feel free to include "you stupid twit, you didn't close your xyz tag" or comments regarding my sloppy code. Ugh. When I get rich I'm just going to pay somebody to do all this for me and make it look fabulous.