Why criteria do lawyers use to select jurors out of members on jury duty?

If the trial was for the rape of a 17 year old and you were close to that age, you might be excused by the prosecution because you might identify with the defendant. Attorneys in a Medicare fraud case might not want you if you were disabled. Attorneys want to win and they want jurors that will vote for their side. I may sound jaded but I believe that justice is not always blind and the good guy does not always win. It's up to you to make the system better.