Why do parallel systems of criminal courts exist at the state and federal levels?

Parallel systems of criminal courts exist at the state and federal levels to address the distinct legal frameworks and jurisdictions that govern different types of offenses. State courts typically handle violations of state laws, while federal courts deal with violations of Federal Laws and constitutional issues. This division allows for a more specialized approach, ensuring that cases are adjudicated within the appropriate legal context, and reflects the federal structure of the U.S. government, where both state and federal authorities have their own powers and responsibilities.