Ki11aWi11, on the one hand, you're right; but on the other - the humanity still can't send manned missions even to the Mars, and hadn't fly even to the Moon near an half of century. And we haven't send such missions to asteroids. But Kerbals have. So, why they can fly to asteroids, to the moons, to the other planets, but can't go to the Jool? The only reason I see is it's monstrous gravity. But I don't think it is overmastering obstacle for green guys, they'll just send heavy rockets to Jool's upper atmoshere non-returnable mission (hardcore) or drone (softcore).