I work in quantitative finance and find that basic probability and statistics help a lot in this field. In fact, they are almost like prerequisites for hiring.
That said, I think everyone would benefit by reading a bit about these subjects, whether or not they’re developers. We seem to have a built-in tendency to underestimate the effect of randomness in life (see Fooled by Randomness and How to Lie with Statistics). To counteract that, I find statistical methods (e.g., hypothesis testing, confidence intervals, etc.) to be very useful tools to keep in mind. Having basic familiarity with such tools may not necessarily make us better programmers but it'll probably make us more rational decision makers in the general sense.
That said, I think everyone would benefit by reading a bit about these subjects, whether or not they’re developers. We seem to have a built-in tendency to underestimate the effect of randomness in life (see Fooled by Randomness and How to Lie with Statistics). To counteract that, I find statistical methods (e.g., hypothesis testing, confidence intervals, etc.) to be very useful tools to keep in mind. Having basic familiarity with such tools may not necessarily make us better programmers but it'll probably make us more rational decision makers in the general sense.