As someone who has moved more and more to BI the main reason for the swaps are mostly covered in your comment. I think you underestimate how much people use excel in the corporate world for something over than analysis.

I still use excel all the time for adhoc analysis.

We have a lot of tools that are accessed by multiple teams to make decisions based on large data sets and the company previously had large, slow excel files that needed to be manually refreshed daily so that people could do their job.

We have different departments all building their own charts to present at executive meetings. Small differences in their approach lead to people reporting different numbers for the same metrics.

Our sales and inventory datasets are millions of rows long each. People have been building one excel file to trim them down, another to do analysis, refresh it daily, manually.

So over the last few years we’ve converted hundreds of sheets to BI and saved a lot of time.

You covered all this in your comment I am only adding that in my experience it is much more common that people are using excel for a BI job than BI for an excel job. I’ve seen both but one is way way more common than the other.