Because they can still be classified.
Uplink is a sim, just a very bad one in terms of reflecting reality.
Darwinia could be argued to be an RTS that focusses largely on territory control, which considering almost all others are "GATHER SHIT, BUILD SHIT, RUIN SHIT, REPEAT" is fairly unique.
Defcon is an RTS which focusses on nothing but damage and damage control; you can have your naval units completely blown out of the water, your buildings could be but a distant memory, but as long as the other guy isn't getting as many kills as you, you're winning.
Multiwinia might as well be likened to Darwinia, there's no reason not to.