I'm not surprised scrollbars are hidden. They're hidden by default on macOS and when you find out that every other OS turns your design into a scrollbar mess, disabling all of them is the quickest fix.
Usability breaks the look of my design, so I'll break usability! Obviously it's more important that everyone sees my amazing graphic design skills, than that they can actually use it!
Usability is one thing, but with Apple hiding scrollbars by default, loads of macOS-designed websites spawn scrollbars all over the place on other platforms because of 1px overflows.