In the first place, the debt ceiling maintains a system of accountability for national debt set up by the Constitution. Lawmakers must go on record as approving an increase in the debt limit in order to enable the government to borrow to fund the spending the lawmakers have approved. They must confront, in a very public manner, the costs of the programs they have enacted.
One of the ways in which government is able to operate unaccountably — that is, outside of democratic checks and balances — is by facilitating public ignorance about its activities. The debt ceiling vote helps raise public awareness about the costs of government, keeping government accountable and increasing democratic participation.