You have many options: stop maximizing your browser window, use a custom stylesheet, use Readability/Readable bookmarklets, etc. I'd guess Groklaw comes from the open source design philosophy, where user freedom (such as to resize the browser window to make the text the width they want) is more important than designer control.
There's any number of browser tools to let you adjust or disable a sites CSS or clean up the articles. I've never had a problem with Groklaw, but on the other hand I do have styles installed for HackerNews to darken the page considerably (dark charcoal background and near white text)... If I read Groklaw more often these days (not so interesting since SCO fell apart) I'd probably have done the same there.
Colors, typography, the massive line-lengths. It's a wall of text. Just an all-round horrible design.