I only worked in finance for a brief time, but the operating procedure at my job was to formulate models in Excel, then validate them in a formal QA environment before using them in production.

I really doubt any major finance player allows someone to whip up a spreadsheet, plug some numbers in and start trading off that information. Excel is valuable in the early stages because it's fast, powerful and easy to collaborate in. Trying to eliminate it just because it's Excel is dogma.