Why do most restaurants fail?

Rarely because the food was bad. Most restaurants that close fail for structural and measurable reasons — a lease the revenue could never carry, a reserve that ran out before the ramp finished, a prime cost above the level the model could sustain — that were visible in the numbers long before the end. Bad luck and bad food get the blame; structure and cash do the killing.

From Why Restaurants Fail: The Honest Reasons, From the Turnaround Chair — the full reading, with the method behind this answer.