What, we're not? But, but - more than tubes that might be turned into weapons, more than simply the notion of possibly buying some spam-advertised yellowcake, there are actually identified fissionable materials involved! There'd be no time-wasting searching around looking for mobile biochem labs, or hidden secrets and fortresses - we could just drive right up to the reactor facilities.
Huh. You'd almost think that was a bug, not a feature. I suppose it is far less of an adventure to go after a set of knowns than it is to run around playing treasure hunt.