Constitutional Length?

My roommate asked me today why everyone’s new constitutions (Afghanistan, Iraq, EU) are book-length-features, when we could make due with two or so pages. This comparison has certainly been remarked upon in the rightblogistan, generally as a subtext for how much better we are.

I tend to think the short Constitution was from a naïve and rather good-willed time, and we are the exception not the rule. These days people are generally unwilling to not address political issues of key importance to them in their founding document. But does anyone else have any knowledge or ideas that might explain this?