For those looking to accessibly scroll webpages: if not visually impaired, could I introduce you to the powerful combination of hitting spacebar to scroll down webpages and (in Firefox, at least) hitting the / (forward slash) key to bring up the "quick search" window? From there, you can type in whatever you want to select or bring into focus that you see on the screen. It's a great way to quickly move the focus to another part of the webpage. (If you just hit tab without quick searching first, you'll scroll back up to the last link that was in focus, but by using the / key quick search, you can basically navigate with just your keyboard and the tab key.) While this doesn't help if scrollbars are embedded in a site, if it's a traditional webpage such as the parent article, it works great :)
As a result, while I do have and use a trackpad, I rarely feel like I'm missing scroll bars because I can just hit spacebar (or page down) to scroll down most times. If you need to page up or down on a Mac, it's fn key + up to go up a page, and fn + down to go down a page. Meanwhile cmd + up is like the Home key and cmd + down is the End key, so you can quickly scroll to the top or bottom of a page (or text entry box).
Not to say this isn't a valid article, but there /are/ workarounds to missing visual scrollbars if you absolutely need this functionality.
Admittedly, these workarounds do not work that well on mobile, where I sometimes wish the iOS Contacts app A-Z scroll helper had somehow "caught on" within webpages, to scroll them. We're missing an IDE-style control that helps us "quick scroll" and jump between headings and sections of longer webpages, that's for sure. As the article mentions, I'd be in support of minimaps, but my version of them would look a bit more like the contacts UI, small icons to represent each section that I could click on to navigate to it, and maybe if I swiped left on the right side of the screen it would show me the table of contents in full, with a search box? (Just spit-balling here, but we need more UI innovation and standardization, not less. I really don't think we've found the "perfect" UI, I think we just forget what made old UIs great when we build new UIs... And sometimes we invent greatness: see the Alfred-like Spotlight search box that you can even get on Windows via power tools that lets you quick switch to any application just by typing its name... literally genius, but not something easily available before OS X Lion.)