All nations within the Anglosphere (US, UK, CA, AU & NZ) have JD imposed towards citizens. I know that the US & Canada both inherited that from Britain, which explains why they have it. However, should it be entirely only the judge making the conviction (some countries operate on a lay-judge system meaning juries aren’t used, such as Finland or Japan for example) rather than leaving that decision up to jurors?
They generally don’t. Juries do not interpret the law, they just look at the evidence for both sides and decide which is right. The judge tells them what the law is. In fact, attorneys for both sides really don’t want lawyers or legal professionals on juries.