Not having a persistently visible scrollbar means there's often no visual signal that something can be scrolled, or what the boundaries of the scrollable view are.
It's especially bad with flat UI design, to the point of being a dark pattern: in the Windows 10 and 11 setup process, there's a screen for opting out of various privacy invasions and other anti-features. Several of the options are completely invisible and undiscoverable until you start turning off the ones that are on screen, changing how tall those options are and revealing that the list is scrollable. Abuse like that is reason enough to always mistrust and hate auto-hiding scrollbars.
Again, disagree. This has it backwards. Microsoft isn't making it hard for you to opt-out because of the auto-hiding scrollbar. They're just taking advantage of it to make it harder in a new way. Before the scroll bar it was nesting it deep within menus.
> Before the scroll bar it was nesting it deep within menus.
I'm not sure which version of Windows you think predated scroll bars, but I'm pretty sure it didn't have any telemetry reporting back to Microsoft over the internet.
> if Microsoft just re-enables those settings when you update windows?
That's another matter entirely. Microsoft's current strategy is to give at least some appearance of getting informed consent for those anti-features. Silently re-enabling them during an update without asking the user would be much more likely to get them in trouble.
It is not another thing. You argue that auto-hiding scroll bars are used by Microsoft to create dark patterns for hiding settings from you. My point is that the problem is Microsoft and not an auto-hiding scroll bar.
“Make it apparent when content is scrollable. Because scroll bars aren’t always visible, it can be helpful to make it obvious when content extends beyond the view. For example, displaying partial content at the edge of a view indicates that there’s more content in that direction. Although most people immediately try scrolling a view to discover if additional content is available, it’s considerate to draw their attention to it.”
Not that simple. Just ran into it today where I was trying to scroll down a page and couldn't. Why? Because there wasn't anything more further down. In the past the scroll bar would of told me there wasn't anything more, but now I actively have to try (and fail) scrolling to 'discover' the fact that there isn't anything there.
You don't need to design your way out of a problem with a custom solution every time if you just add the scroll bar.
Being fooled into believing there's no more content is often incidental: some gap in the content aligns perfectly with the bottom of the window. (This is especially the case with designer websites which use a lot of blank spaces.) You shouldn't need a custom solution.
I wouldn’t consider having the website be designed to let you know that there’s more content a “custom solution”.
As for the rest of your comment. This really is a matter of preference. You’ve built a habit to look at the scroll bar. I’ve built a habit to try scrolling and see what happens.
It's especially bad with flat UI design, to the point of being a dark pattern: in the Windows 10 and 11 setup process, there's a screen for opting out of various privacy invasions and other anti-features. Several of the options are completely invisible and undiscoverable until you start turning off the ones that are on screen, changing how tall those options are and revealing that the list is scrollable. Abuse like that is reason enough to always mistrust and hate auto-hiding scrollbars.