To say that Excel is as dominant as it is today in casual business programming because of the meager amount that’s taught in schools does a disservice to the fact to how damn powerful it is. It’s Microsoft’s Emacs!
But you sort of made my point by comparing it to emacs.
Open source (or at _least_ open formats) can be incredibly powerful. Unless you’re claiming that Excel could only come into existence because it’s proprietary; in which case I don’t understand.
Excel has an incredibly strong pull because it's been integrated onto a lot of learning material now, and because it barely changes any old features. When I joined in PE a few years back, one of the study materials provided to us dated back to 2000. The videos shown used shortcuts, features and formula that are still used today. Even now, finance guys remember those keyboard shortcuts from those old videos like they are mantras or nursery rhymes - especially when knowing those shortcuts or features let's you go home by 10 instead of 2 (this was a line in the training video actually lol).
My point was to reason why Excel has a strong pull compared to Emacs. They locked in customers early on, then coupled with backwards compatibility, ensured that everyone kept using it. Which is why GSheets barely made a dent on Excel, even though it had much needed collaboration early on.
Why would you use something other than what every new potential employee is familiar with?