What's The Point of a Debt Ceiling?

Now that the Dems are lifting the debt ceiling it makes me wonder what the point is of having a debt ceiling in the first place?  Isn't the debt ceiling supposed to prevent Congress from spending and, more importantly, borrowing as much as they want?

If Congress is able to lift it when they feel the need to shop, and splurge, then why have it?  It's like increasing your credit card limit whenever you want, you just call up the credit card company and tell them you want to raise your limit!

In matter of fact, it's EXACTLY like that!  The Dems should get some cojones and just ABOLISH the debt ceiling and stop making believe it means anything to them!