With Excel any reasonably capable business analyst can do sophisticated calculations quickly without needing anything else. With a web app, SQL database and whatever the ramp up cost is huge in comparison.
With Excel I can do things fast, at the beginning, but then I find that it get a bit more tricky, I get lost, I find out that things are wrong, I do more, I want to move to R. I can't move to R. It will take me a week. I have a day. Then I want to move to R, it will take me a month, I have a week, then I want to move to R, it will take me a year, I have a month. Then, I want to drink bleach.
I disagree. I am working on something right now at my employer where we are taking spreadsheets that have been used for quite a long time (and were created fairly quickly) and they are converting all the business logic to code. Each workbook is taking weeks for them to code and test and then send back to us to sign off on.
I'm a coder DOING some of these conversions. I see both sides of the coin here. One additional point I wanted to mention is that once we have done one or two, or a dozen of these conversions, we start to see common themes.
More often than expected, there are mistakes and misunderstandings in some of the spreadsheets. There are inconsistencies in the spreadsheets. In IT we also get calls that a spreadsheet is "locked by someone." Or that someone deleted a spreadsheet.
With code, and databases, we can ensure consistency between operators. We can also leverage the data across other applications since it lives in a database now. We can pull reports for management more easily, and with more automation.
As some other comments mentioned, spreadsheets are great for prototyping, but also have their drawbacks.
