Getting grants counts positively in an academic’s evaluation and results in promotions and raises. But grants are supposed to be inputs for research, not outputs. Other things equal, it should be preferable to get the same output with fewer inputs (more efficiently and cheaply). Given an academic’s publications and patents, the grants they received in order to create these outputs should count negatively in their evaluation. The university administration is interested in motivating grant-getting, because they tax the grants – take a fraction of each for themselves. The motivating is done by promotions and raises. Rewarding more use of inputs inflates the cost of research and diverts effort from scientific output to getting more inputs.
A justification for rewarding grant-getting is that having current grants makes it easier to do research, thus increasing the expected scientific output in the near future. This only applies to a person’s current grants, not those already spent. Perhaps the current grants may count positively in an evaluation, but the spent ones should still have negative weight.
Once the system is in place, there may be an additional incentive to follow it: signalling obedience to rules. If academics are expected to apply for grants, then the ones that publicly do not may be considered contrarian, which may have negative consequences.
A similar reasoning applies to researchers from rich and poor institutions. If university resources are used for the work, then the person from a rich institution had more inputs for their work. The same output from a scientist in a poor university should be a more favourable signal about them.
An analogous adjustment is done in US college applications when low socioeconomic status confers an advantage. The direction of the correction is right, but its appropriate size remains to be determined.