The technobabble seems to indicate that mounting both a Hopper and a Jump drive to a ship is a bad idea. First of all they're both bulky power-eaters, which means that despite all attempts to miniaturize them, carrying both types of engine would mean less space and power available for propulsion, shields, and weapons. Second and probably more important is that supposedly the residual radiation left after a "hop" that prevents the Hopper drive from being used again until it disappates has the same effect on a Jump drive--you wouldn't be able to Jump OR Hop for a few hours after a Hop.
Of course, the most important reason is plot. It wouldn't do for storytelling for a Confed ship to be able to suddenly "hop" away from danger unless the Kilrathi ships stood a chance of being able to pursue it.
Of course, the most important reason is plot. It wouldn't do for storytelling for a Confed ship to be able to suddenly "hop" away from danger unless the Kilrathi ships stood a chance of being able to pursue it.