I think mouse users don't generally suffer from this problem: by default, MacOS always shows a scrollbar in all contexts if you have a mouse plugged in to your computer.
A customer of mine was surprised to see some extra VMs in vSphere a few days ago. He never tried to scroll a list somewhere in the app and always missed the extra content because his Mac doesn't display the scrollbar. He has a laptop, so no mouse. I tweaked my Gnome desktop to always display a transparent scrollbar (only the outline is visible) so I could see that the list had extra elements.
By the way, vSphere is part of the problem. It's one of those web applications that try very hard to look like a desktop application. It doesn't use the standard HTML behavior of building a page that scrolls. It clips everything at the borders of the screen. Ironically that reduced functionality probably cost them a lot of developer time.
Not only does it not show the scroll bar by default, but (not sure if this is a Chrome or Mac issue), when it does show up during a scroll operation, you have to have great reflexes to grab it with a click if you want to.
