I have some 4k pixels of width on my desktop, and some 400 on mobile. It makes sense to not have a wide scrollbar on mobile. But it makes zero sense on desktop.
Scrollbars do two things. They let you scroll (duh), but they are also progress indicators. There are other ways of scrolling (e.g. swiping on mobile) which work by default. But there is no other default way of showing progress. I don't particularly like the progress bar example in the original post, something as unobtrusive as a percentage in the bottom right corner would work just as well. But I do want some indication of progress ...
Agreeing strongly, but I'd just like to point out that a probably more significant problem on mobile is that a scrollbar which you're likely to unintentionally hit with your fingers as you're clumsily and very imprecisely interacting with your device, or as Steve Jobs so famously declared, are "holding it wrong", absolutely is a valid reason to deprecate classic indicator-and-control scrollbars on mobile devices.
That is, a classic desktop scrollbar, dating back to Xaw widgets, the original Apple desktop, and even earlier[1] not only shows where you are within a text or display, but allows you to control where you are typically by clicking on elements of that scrollbar: the cursor, the bar itself, and the endpoint arrows. Several of these had interesting / quirky / annoying variants on interaction (those familiar with early X11 Xaw widgets can likely think of several).
There's an interesting static image comparison at Reddit:
Another point on swiping: my mobile device for the past three years has been an e-ink tablet. And I've learnt that swiping absolutely sucks. E-ink displays are much faster than people seem to believe, but there's still lag that an emissive display lacks, and it's far better to page through a long text or display than to scroll through it. I've all but entirely adopted an e-ink optimised browser that mostly does this, EinkBro (based on FOSS Browser), and I am constantly trying to page through other apps by tapping where EinkBro's forward/back touch zones are. People who've used other ebook readers will be familiar with the general concept as most have similar features. Having to imprecisely scroll through a document or app is exceedingly painful.
Scrollbars partially solve this problem as for most, tapping above or below the cursor will advance the display by about a page of text (some feature a few percent overlap). On desktop systems, there's an even better option: the space bar. For a whole slew of apps and tools, dating back to Unix's pg, more, less, most, etc., you can page through a long text one screen at a time by tapping the space bar, which is the largest damned key (and hence the easiest-to-hit target) on the keyboard (Fitts's Law[2]).
By contrast, scrolling on mobile:
- Is highly subject to the tap-vs-drag confusion: the GUI cannot consistently distinguish a tap action (interacting with the application) with a drag (changing the viewpoint).
- Is imprecise both by contact point (that is where you're interacting with the display) and displacement amount (how far you're moving through a text or app). You might scroll by more or less than a page, and it takes considerable time for the eye to recapture the reading point.
- Obscures what it is you're interacting with. Your finger is covering the display you're trying to manipulate. A desktop mouse cursor by contrast covers little or none of the text or app.
- Is subject to further confusion based on dynamic characteristics of the document or app you're dealing with (e.g., a Web page with progressively-loaded or rendered elements, or on Mozilla Pocket, inconsistent placement and textblock wrapping around image elements).
I come to desperately hate scroll-based interfaces these days.
Scrollbars do two things. They let you scroll (duh), but they are also progress indicators. There are other ways of scrolling (e.g. swiping on mobile) which work by default. But there is no other default way of showing progress. I don't particularly like the progress bar example in the original post, something as unobtrusive as a percentage in the bottom right corner would work just as well. But I do want some indication of progress ...