I wonder what percentage of CSV represented data 1) passes through a spreadsheet at some point from data source to final data consumption and 2) how much of tha

I wonder what percentage of CSV represented data 1) passes through a spreadsheet at some point from data source to final data consumption and 2) how much of that spreadsheet action is specifically MS Excel. You're right, there is no standard that I'm aware of, though the answer to those first two questions could well be a proxy for a de facto standard in practice.