For better or worse, users still tend to scan a website in an F-shaped pattern:
The implications of this [F-shaped reading] pattern are:
First lines of text on a page receive more gazes than subsequent lines of text on the same page.
First few words on the left of each line of text receive more fixations than subsequent words on the same line.
In other words, whatever is placed in towards the top-left of a page receives the most (intial) attention, so it's good practice to place the important items in that area, such as the main navigation. Which, in turn, means that less important items should be placed in a different location on the page, and this also applies to the less-often-used utility navigation.
This doesn't mean that you should never place utility navigation in the top left, but it might distract the user from more important content, so tucking it away towards the right still keeps it highly visible without letting it compete with more important stuff.
P.S.: The above applies to locales with left-to-right scripts; for locales with right-to-left scripts, the opposite applies, of course.