Fixed vs fluid - what type of layout to choose?

I browse in a wide-screen monitor, and while I don't maximize my browser window, I do make it wider than most standard fixed widths. So it's always interesting to me to read the many discussions on whether to use fixed width or flexible/liquid/fluid width layouts. It's especially interesting that while most polls I see on the question indicate that most designers prefer flexible width layouts, most pages that I visit are a fixed width. They might be elastic (having a fixed maximum or minimum width that scales to browser sizes - that's what the About.com pages are like. Don't believe me? Make your browser window smaller and then reload my home page. It goes from 3 columns to 2.), but elastic widths are hard to recognize as they look like fixed width layouts above their maximum width. I guess what I'm asking is this: why is it that people profess to prefer flexible width layouts, but so few layouts actually fill my browser window? Personally, I prefer to write elastic layouts up to a maximum of about 1200 px wide. My concern is less with the width of the entire page as much as the width of the content sections. Columns that are more than 7-10 words wide or less than 2-3 words wide are hard to read. So I focus on making those columns a fixed width, and try to have everything else flow around them. I don't like being forced to use either fixed or flexible width layouts because there are pros and cons to each.