LunchBox, I was thinking the same thing!
Not many people know, but it's been often wondered why it took so long for the Empire to build the Deathstar v.1.0.
Answer: They didn't have the tractor beam technology ready until sometime between episodes III - IV.
You didn't see tractor beams being used in Ep.I-III, did you. That's because not until the massive resources put into military technology by the empire were they able build tractor beams.
Interestingly enough, repulsion technology was already widely used during Ep.I-III. One might think making a tractor beam would be just "reversing" a repulsory field, but maybe it's not that simple.
