What is the Rules Enabling Act? I understand it is congress allowing the courts to make rules, but why does congress have to give that power to the courts? I thought the courts were independent, one of three co-equal branches?
Prior to that act, civil procedure in federal courts was non-uniform (historical overview). The main problem seems to be that courts were supposed to conform to the procedure of the state in which the court is located (as mandated by the Conformity Act of 1872). The "has to" reason is that SCOTUS at the time did not feel that it was authorized by the Constitution to write its own rules when Congress could have done so, see Wright & Miller Federal Practice and Procedure. The root problems seems to be the Process Acts of 1789 and 1792, which in the latter case did not allow courts to set rules for actions at law, and in the former case required courts to apply rules in effect when the state joined the Union (regardless of how the rules changed subsequently).