I have come to a funny realisation recently. It's not my eyesight which is becoming worse, it's the UIs which are becoming worse. The tiny scrollbars with laughable contrast are in no way accessible to anyone. I've recently switched to using KDE with the Oxygen theme and it's a joy to use without any eye strain. These scrollbars are absolutely pathetic, with no room for customisation. (good luck theming a locked-down…
If we are talking UI we need to talk about Apple. The first thin I do on MacOS is turn on the scroll bars. Yes, MacOS Has them set as "Only Show When Scrolling" by default, which is probably the most ridiculous setting.
Not having them take up screen real estate and working with most people's usage styles while being configurable for others is the right decision. The problem is systems and applications that don't let you configure them.
People talk about accessibility and their preferences like they are absolute truths— it's a lot more complex. Not having scroll bars sucks for people that never got comfortable with other scrolling input methods and people who use sight interfaces, for example. They couldn't possibly be less relevant to people who use screen readers, and as an input method rather than an Univision visual indicator, only slightly more relevant to people on phones and tablets. Phone and tablet usage has outpaced regular computer usage for quite some time, and that informs users interaction style. Adding visible UI elements adds cognitive load, and for people who never worked with scroll bars out of necessity, they're just another bulky animated distraction on the screen. Most younger users would probably think them about as useful as an always-visible on-screen keyboard.
I guarantee you— the designers at Apple who chose to hide those scroll bars probably thought more about scrolling more than every one of these commenters combined, and that was before they did formal usability studies.