It's mentally agitating when I go to scroll on a webpage and it doesn't do what I expect.
And what content authors should be most concerned about: it distracts viewers from the site's content, because I'm thinking "what just happened to my mouse". And that reaction is the antithesis of what content creators should want: they should want to engage me, and explore the site more deeply.
My follow-on guess is that management figures you're scrolling past the adds too quickly.
Though we’re at the point where browsers really need to clearly separate what requires advanced capabilities from what really doesn’t. For example, a browser could always display exactly two tabs per page: “Read” and “Interact”, where ONLY the Interact view can access scripting capabilities and dynamic content and the Read view may only display trivial things like images and text. If you’ve ever installed something like uMatrix on the desktop (and you should), it is astounding how much crap from how many entirely different domains is loaded and executed just by loading a “simple” page now. It has to stop.
There are some, like I believe most Apple product pages, where scroll-jacking is used to create a one-slide-at-a-time-effect where it may work. But even on those, individual slides often undergo transformations upon scroll revealing information you'd otherwise not see.
The browser creators, people paying for websites, and (many) javascript developers all seem happy with this, unfortunately.