Well, sure, no such station currently exists. But there is science fiction of the "we could do it if someone just ponied up enough $$$" variety, and then there is the other sort ("we just need to invent anti-gravity, and we are all set").
And to me, a rotation space station would seem to squarely fall into the first camp - unless there are some fundamental engineering issues I am not aware of. But my assumption is that all that is keeping us from building something like that, and putting it in orbit, is the combination of the staggering price tag, and the questionable utility of a low orbit space habitat. As in: it would cost astronomical sums of money to build - but for what do we need this sort of thing, exactly?