Should motorized bicycles be illegal?

Should those small motorized bikes that come in a kit be legal to drive without a license? In Ontario electric ones are legal with no license why not gas ones too? They are lighter, and travel around the same speed and the "E" bikes are no less "motorized" than one with an electric motor. As long as you drive responsibly, respect other drivers, and obey traffic laws should there be a penalty for operating one?