Well, it does indicate which parts of your site are intuitive vs in need of improvement if you can see where people click and how long they spend looking at a given portion of the page.
But, like others have said, it's of questionable utility in the age of smartphones on websites that don't break the established design patterns, so I pretty much agree entirely that it's unnecessarily invasive. At least, for my site!
How much of a difference does company size make, when gauging the impact of individual words? Because it sounds like it's a problem to spend millions on, when millions are a few percent of sales and fractions matter. Surely individual words aren't the path from ~$100 monthly revenue to tens of thousands?