A social planner might induce effort and risk by paying large bonuses for major results.
But given any budget to allocate among researchers, this is inefficient from the researchers' perspective because risk aversion means that to increase the utility of a high earner even modestly, you have to take a lot of wages away from low earners at high utility cost.
But here's the thing: science has no external social planner.
Scientists themselves determine what results are considered worthwhile, and how worthwhile. They decide who is hired, promoted, given wages, is awarded prizes, and garners esteem. In other words, they set their own wages, of course subject to a budget constraint.