Even though they were developed to help simplify an analysis, scoring and indexing systems actually add an unnecessary level of complexity and obscurity to a risk assessment.
Statistics-centric QRA’s suffer from lack of specificity to the assets being assessed.
Numerical estimates of risk – a measure of some consequence over time and space, like ‘failures per mile-year’ – are the most meaningful measures of risk we can create. Anything less is a compromise. Compromises lead to inaccuracies; inaccuracies lead to diminished decision making, leading to mis-allocation of resources, and leading to more risk than is necessary. Good risk estimates are gold. If you can get the most meaningful numbers at the same cost as compromise measures, why would you settle for less?