Unlike the other domains, the two following sites do not have a meta/parent cross-link at the top of the page:
It'd be nice to have a consistent interface. At the top is a good place.
It looks like this has been changed now. Now there is a parent/meta link between Stack Overflow and Meta Stack Overflow.
My original answer remains below; I still hold the same perspective.
This is primarily because Meta Stack Overflow does not have a direct Parent/Meta relationship with Stack Overflow, like what the rest of the site pairs have.
Meta Stack Overflow, while it serves in the stead of Stack Overflow's meta site, is also the meta site for the Stack Exchange Network as a whole. One could envision it as Stack Overflow Internet Services Inc.'s Meta. This is why it gets its own special Meta link in the footer, unlike every other Meta site.
It is also mechanically different - it does not carry over reputation from Stack Overflow and operates basically as its own independent site. So ultimately, creating a faux parent/meta relationship would be misleading.