Most developed countries have programs to support research and encourage students to choose careers in it. This suggests scientists have a positive externality on the rest of their country that is not fully internalized in their income. Why not support research by paying the researchers its value, assuming the value can be measured? This would internalize the externality, leading to efficient effort provision.
A potential answer is different risk aversion of the organization supporting science and the scientists. If the institution is involved with many different projects, it is diversified and likely to be less risk averse than a researcher who only has a few projects. The arrangement optimal for both sides is then for the institution to offer insurance (at a cost). The researchers get paid a lower expected amount than the value of their work, but with a lower variance. Instead of the scientists taking loans to finance their work, becoming rich if the project succeeds and bankrupt if it fails, they avoid loans and get a fairly constant salary.
There is a tradeoff between incentives and insurance. If the salary does not depend on success, there is no incentive for effort, but perfect insurance. Having researchers take loans and get the full value of their work provides no insurance, but strong motivation. The compromise is that promotion and pay depend somewhat on research success, but not too much.