Yeah, that was the first one my eyes went to. The only scenarios I can think of where it is acceptable to hide scrollbars are infinite canvases where you’ll draw your own non-linear ones (and even then be disappointed because they can’t look or behave natively), and things like maps where you remap scrolling to zoom and might want to use a backing invisible scroll area for that rather than consuming scroll events (which are somewhat more limited).

In short: unless the native scroll bar will be wrong, do not under any circumstances hide it.