As for "who typically offers this" I would argue that this isn't quite like a "normal" time. Many people are putting their health on the line to come to work which is not something that is normally part of the decisionmaking process for their regular wage. As a result of that increased risk and because of the huge demand for their labor a large increase in pay makes a lot of sense (even if we take the "combat pay" stuff out of the equation. Demand-alone would increase their wages)
As for "who typically offers this" I would argue that this isn't quite like a "normal" time. Many people are putting their health on the line to come to work which is not something that is normally part of the decisionmaking process for their regular wage. As a result of that increased risk and because of the huge demand for their labor a large increase in pay makes a lot of sense (even if we take the "combat pay" stuff out of the equation. Demand-alone would increase their wages)