Why might Congress pass a continuing resolution?

The federal deficit has grown so large that interest payments on debt now take up a sizable portion of the budget, so Congress needs to raise taxes.

Congress has not passed the federal budget in time, and so it decides to set spending for the coming year at the same level as the year before.

The level of discretionary spending in the federal budget has become exorbitant, so Congress needs to cut funding to national defense and infrastructure maintenance.

The president has vetoed all appropriations bills created by Congress, and so Congress decides to override the presidential veto.