Former British colonies are using Common Law. Other democratic countries are using Civil Law. Common Law == Jury, Civil Law == Judges.

The requirement that it goes through jurors who are your peers is the point. The requirement came from where a judge appointed by the King might not be fully trusted to act in the public's interests, but the King's interest. The ability to judge someone guilty devolved to a jury because it was a lot easier to do this than any other form of check on judicial power.

Not only for the obvious reason (or, well, the one I think is obvious), but also because tons of crimes go unreported or never followed up on because the system doesn't think it will get a conviction and lower the rates. This includes rape and sexual assault.