With all due respect, I am going to back out of this debate. I originally posted to correct you on whether the United States requires jury trials. I then posted to give you the Court's reasoning as to why it came to this conclusion on federal rules of criminal procedure (which affect very few criminal cases overall). I did not, nor do I, intend to get into a social policy debate on the rules of criminal procedure.
Nonetheless, I will point out, as someone with a bit more specialization in the American Criminal system, that your conclusion requires a lot of assumptions (which may or may not be correct) and over simplifies the prosecution's mindset. In essence, and speaking as someone with a disgust for prosecutors, there are many reasons that a prosecutor may not want a jury as a matter of principle: (1) jury nullification, (2) hung jury means retrial, with the defendant knowing your witnesses and arguments, (3) jurors might not fully understand the law as well as a lone judge, (4) a judge is better at evaluating the facts and excluding prejudicial evidence than a jury, should it come out, and (5) there are about 15 judges per federal district court, which means more predictability to learn and appeal to idiosyncrasies than 12 randomly selected jurors (and federal jurors come from a larger geographic area than state jurors). Again, not intending to debate, just pointing out that your internal reasoning might look attractive on paper, but ignores legal realities.