That's pretty subjective. Why would that be the "best" link?
That would be my thinking. Ok so maybe wikipedia doesn't have to be the top result, but I'd rather have results relating to the thing I'm searching for come above sites just named after it.
"define ford" shows a dictionary definition of ford before all results, "define stack overflow" shows a link to wikipedia before all results.
Of course with the imprecise and constantly moving nature of language this is not easy.
I'm really just expressing a preference :)