“Excel made a whole new style of working possible for the financial industry in two ways. First, it facilitated the creation of much bigger and more detailed financial models; in the days when you had to fill everything in yourself having worked it out on a pocket calculator, you would really think twice about whether you really needed to estimate staff costs separately from other costs, let alone about how many divisions and geographies you were going to model for big companies.
But much more importantly, it allowed you to work iteratively. Rather than thinking about what assumptions made the most business sense, then sitting down to project them, Excel encouraged you to just set out the forecasts, then sit around tweaking the assumptions up and down until you got an answer you could live with”
https://backofmind.substack.com/p/the-spreadsheet-revolution