Too bad Google once again leads the way of being a prominent example of a bad idea with its custom scroll bars on many of its properties.
Then they went to Lion and ruined them: grey and almost invisible by design. Magical mystery popping into existence when you hover where it ought to be. Probably. I think this is when they inverted the magic mouse scroll behaviour to pretend like your iMac was an iPhone.
The backwards scrolling is way more obnoxious though, and I rage every time I use someone else's Mac or do a fresh install.
Most of the times I encounter backward scrolling on someone else's Mac, it's only there because they never realised Settings let you invert it to sane and useful!
People switching back and forth between Macs and iPhones or iPads initially found it very inconvenient/frustrating to have window scrolling on a touchpad and content scrolling on a touchscreen.
It was decided that switching the Mac to be consistent with iOS would cause momentary frustration for Mac users (it requires a few days of retraining to get used to) but would be less frustrating for most users than preserving two inconsistent behaviors into perpetuity.
The option to keep the Mac on window scrolling was included to mollify those few Mac users unwilling to spend a few days or weeks re-training themselves to a reversed gesture.
If you do have a problem, then you can switch it in System Preferences. Everyone wins.
These are UI/UX conventions. Everything is "pretend".
For example, users whose mental model of scrolling tracks the viewport will want to scroll up to move the content down. The viewport goes in the opposite direction of the content.
Fair enough.
However such users don't seem to want the same for horizontal scrolling. Tracking the viewport left moves the content to the right and vice versa. But horizontal scrolling in macOS always tracks the content regardless of the setting in System Preferences > Trakcpad > Scroll direction: Natural.
The exception (turning it off for "inverted" scrolling or "viewport tracking") is only for vertical scrolling, not horizontal, which suggests the mental model can be adapted though users who prefer viewport tracking report they cannot adjust.
Of the few people I've bumped into who had it set to natural, and had for some considerable time, well even those were happy to learn it could be changed, and didn't want to go back. So there's probably something makes it feel odd, and stay feeling odd, for many. What I couldn't say, but not just restricted to those who spent time on other platforms too, like me. Of people whose machines I get to use from time to time at work, they're all set to unnatural too. We're nearly all iPhone users. So it's not just me being odd and rare edge case. :)
Personally, I don't want the same mental model between phone and desktop, as the metaphors are different. UI should look different, act different, suited to using each device. The Win 8 on, Lion on desire to make my laptop "feel" more like a mobile, continues to feel like a huge mistake.
I don't think this is correct.
The setting affects both vertical and horizontal scrolling.
That's the crux of the problem: the only time a website makes changes to the scrollbar is when the author thinks it makes sense.
I just disagree all of the time.
For every other regular site, and even most web apps, I always prefer native, for Windows.
Applications should respect the DE settings for UI. Browsers are the main culprits here, but only because CAD software isn't widely used. Oh, and there's MS Office, that will respect absolutely nothing. All of those are in the wrong. But everywhere the DE is powerless to enforce its style onto applications, so this is a much harder problem to fix;