Why do a legislative branch exists?

Answer 1

The United States is a country founded on law, rather than religion or heredity, and the legislative branch makes the laws which are presented in the form of "bills". Article I, Section 8 of the United States Constitution spells out specifically what Congress (the Legislative branch) may do (enumerated powers) and the last clause states: "[Congress shall have the power] To make all laws which shall be necessary and proper* for carrying into execution the foregoing Powers, and all other Powers vested by this Constitution in the Government of The United states, or in any Department or Office thereof." *this is called the "necessary and proper" clause and is controversial due to the apparent lack of oversight; the Congress, who makes the laws, is also the body that empowers it to carry out the laws it has made. But there is "judicial review" by the Supreme Court and that is another topic...