Well in my case it's probably because generally I don't give two shits about the story to a video game. Uncharted 2 was the notable execption because that story drew me in. And while I enjoy some of the extra storyline and some of the chatting, usually it just goes on a bit too long for me. Listening to that lunatic Seth rant while driving his wagon to the mission was pretty annoying. 
EDIT TO ADD: Part of my displeasure probably has a little to do with some of the voice acting. In particular, the person voicing Bonnie McFarlane I found to be particularly grating and couldn't wait for her to shut up.

EDIT TO ADD: Part of my displeasure probably has a little to do with some of the voice acting. In particular, the person voicing Bonnie McFarlane I found to be particularly grating and couldn't wait for her to shut up.