Progress indication among others. But this is actually the only one retained by current simplified, slimmed and autohiding scrollbars.

Here are others:

-Discoverability: Is there more content? (Scrollbar enabled/disabled) How much? (Size of scrollbar)

-Jumping to a location in the content

-Skimming by hyperfast scrolling

-Coasting by holding a scroll button pressed (this one is forever lost because the buttons have been abolished

-Providing a space for bookmark indicators/in-page search result indicators

There are probably other use cases too.

1. Position of elevator (the little thumb you traditionally drag up or down) shows where I'm at relative to the beginning and end of the content.

2. Size of elevator in relation to the scrollbar tells me what percentage of the content is viewable (except when the size of the elevator becomes so small it makes it unusable).

3. Up and down buttons allow a simple way to bring the next or previous item into view.

A lot of the hate of scrollbars comes from the web, where browser scrollbars could not be styled and didn't necessarily use the operating system's style. You could have a beautiful page be ruined by the default windows 3.11 style scrollbars in the browser.

Your list is missing an entry:

0. The existence of a scrollbar tells you there's something to be scrolled.

Flat UIs are pretty good at accidentally hiding the fact that not all of the content fits on screen on in whatever borderless frame.

It's always fun when the content layout naturally fits into the viewport in such a way to make it look like there's nothing down below.

Also fun when websites that are waging their holy war against the bars don't anticipate that I'm zoomed in a bit. Having to delve into devtools to disable "overflow: hidden" is a delight.

Whats worse is when a website has a footer but they have a never-ending scroll div between the header and footer so as you approach the footer more content loads pushing the footer even further down.

Just this year I was trying to explain to mom how to do something with an iPhone.

There’s about a million different secret handshakes and gestures in iOS UI, but I consider the most egregious UI failure to be the “Share” button, which manages to pop up a modal in such a way that it often disguises both that it can be be scrolled vertically AND that it can be scrolled horizontally.

Don't forget the near religious debate that is scrollbar snapback: skim a document backwards to review an earlier point, or forwards to determine if it's worth further time investment, and then release the mouse button outside the scroll area so that you can snapback and continue where you left off.

Where is this feature available or implemented? I just tried in Chrome and Powerpoint, neither has this feature.

I've never seen an app that didn't have that feature. Chrome included. I don't have powerpoint around to test at the moment. I've been using this feature since the 90s, and I'd miss it sorely if it were to be disappeared.

I try it just now and it works on Firefox & Window's File Explorer.

Somehow I have never discovered this feature. It's brilliant. Thanks!

I can’t figure out if this is parody or not.

In case it isn’t, scroll bars are for quickly figuring out the scope, for quick positioning and for remembering where in the article things are.

> now that we have mouse wheels?

* Horizontal scrolling

* Scrolling when using pen/touch input on non-touch UIs

* Making it obvious that a content area is scrollable

* Providing context into how much content is visible vs. hidden, and where you are in the document

* Making it easy to scroll to a precise location without sitting there twiddling the wheel for minutes to go through something long

> My view is that content is king and any UI element that needlessly takes away space from the content needs to be destroyed.

Your view makes sense at 640x480. Maybe on a mobile screen. On a widescreen computer display, there's plenty of space for elegant UI controls.

Scrollbars are all about physicality. We are creatures fundamentally rooted in a physical world and we think in ways that are deeply connected to spatial properties of the things we interact with. Scrollbars reflect many of these properties in a natural way on a limited 2D plane (as demonstrated by all the other comments). Mouse wheels aren't able to replace that function in any way. It's not their purpose.

Indicating where you are on the page, and indicating that content can be scrolled. (I've seen webpages where there's content "below the fold" but where it's extremely easy to miss that depending on your screen size.)

Scroll bars are a position getter and setter.

Content is king, but kings have all sorts of people supporting them. In fact you can immediately tell who's the king not by how solitary and unencumbered he is but by how much clutter and commotion and how many attendants are around him. I realize I'm pushing the analogy too far.

Progress indication and scrollability indication. I'd actually like to see scrollbars enhanced rather than diminished. So for example I would love to see indicators of headings or breaks or page bookmarks. The latter could even be clickable.

I agree! A lot of code editors are using them in a nice way to display version control info or errors/warnings. Chrome is using it to a small extent when searching using Ctrl-F, showing where in the page the results are. In both cases it's super effective. But they are definitely still underused.

Being able to click to go directly some porportion of the way through then fine tune, instead of having to scroll through all the intervening space.

My time is valuable. How much more of this do I have to read? That's the question scrollbars answer.