I work on a quantitative user research team, and we've found notebooks to be really useful for crunching and visualizing the data from experiments we've run.

I work at Google and my UXR colleagues are more comfortable with Python than JS, so we use Google Colab, but I'd use Observable if those weren't true.

yeah, I know notebooks are used broadly (used them for years myself). I just haven't run into companies using Observable specifically in the wild.