Most of these progress bars are as thin as the native scrollbars have gotten (or thinner). If these are solely a consequence to the shrinking of the scrollbar,

Most of these progress bars are as thin as the native scrollbars have gotten (or thinner). If these are solely a consequence to the shrinking of the scrollbar, you'd imagine that they'd actually be bigger. I think that's a large contributing factor, but either most implementations are are as deficient [0] as what they are trying to augment or there are other things at play here. (Branding since websites haven't been able to consistently style browser scrollbars since the IE/early Firefox era; as the other comment points out, trying to counterbalance how long pages have gotten with "after-content" such as ads and comments and recommended articles and "infinite scroll" to more articles.) [0] Or arguably worse deficient: Most of them seem to have no real accessibility themselves and are opaque to things like screen readers. Even if modern scroll bars are hidden by default and woefully tiny visually by default, they still have decades of accessibility baked in and accessible options (if you can find them).