system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why does the U.S. have a debt ceiling if it just gets raised every few months? Isn't it redundant?
gpt
Before 1917 Congress specified the details of financing in every spending bill.  A bill authorizing the Navy to spend $10 million on new ships would also specify the term and interest rate of the bonds that would be sold to raise the money.  In 1917, Congress passed a bill that authorized the Treasury department to issue bonds as needed to fund the spending authorized by Congress. This bill included a limit on how much debt the Treasury department could issue.   A practice that is still followed almost 100 years later. 

It is redundant in that Congress already controls spending via legislation.  If our nation actually hits the debt ceiling, it would force a default on our obligations and most likely create an economic crisis. In a rational world, the debt ceiling would be eliminated.