Well, I've never worked in finance, but if these are like the mathematical models that I used to make predictions in grad school and for the year after grad school when I worked as a statistical analyst, I do. I presume these are predictive mathematical models, used for forecasting?

Why in the world would Python or R be inadequate for that type of work, if that's what you're implying? What do you think they lack that Excel has, other than a friendly GUI interface? Or SAS, Stata, or SPSS (all of whom have versions that they market heavily toward finance).