I'm building an open-core spreadsheet currently, and pivot tables are by far our number-one data transformation feature. By like 3x-1x. This is compared to even formulas (shockingly! but this is also a function of our audience).

In the hundreds of data-science-in-Excel files I've seen, I can't think of a single one that doesn't make use of a pivot table in some way.

(https://trymito.io, if you're interested)