With one sensor you have no choice but to simply trust the reading and hope for the best. With two sensors you can compare, and if they disagree beyond some ep

With one sensor you have no choice but to simply trust the reading and hope for the best. With two sensors you can compare, and if they disagree beyond some epsilon of tolerance you can fail safe by deactivating the system. With three sensors, you can compare them, and if one is out of bounds vs the other two, you can fail operational by continuing to operate the system while also alerting the operator to the needed maintenance.