I have to pile onto the criticism of the hidden scroll bars, and other similar features (like the hidden buttons of PDF viewers now, such as in Chrome). Discoverability is a problem. For anyone (cough, elderly parents) who aren't adept at discovering hidden features, these things can be utterly mind-boggling and frustrating. Even I was stumped for a good minute the first time trying to print/save/download a PDF when…
There has always been a struggle with UX design, people want simplicity but at the same time they want clarity and complexity of ideas. People want great knowledge, but they don't want to read about the nuances that makes it a great knowledge. There are valid reasons for both sides of the equation, it is just difficult to find the balance to satisfied the myriad of different perspectives.
We used to achieve this balance with a manual.
A printed manual. Not a URL printed in 3 point Helvetica in light gray on a white background on a tiny leaflet in amongst a dozen similar-looking regulatory leaflets that will all go into the recycling bin when the new shiny shows up.