Why is the scroll bar in Windows 11 so narrow? In what world is this an improvement?

The registry fix that K0MB described does not fix the VERY SERIOUS unresolved problem that the scrollbar width on core system apps such as the File Explorer app is way too small even to be suitable for people who have no serious medical accessibility issues. The registry fix that I repeat below only seems to affect the width of the scrollbar in apps that are not core system apps, for example browsers, but does not improve the scroll bar size of File Explorer.

I quote the registry fix that does NOT FIX core system apps such as File Explorer etc scrollbar widths.

HKEY_CURRENT_USER\Control Panel\Desktop\WindowMetrics.
Modify the ScrollHeight and ScrollWidth values

"Windows 11 aims to provide a sleek and modern user interface. Narrower scroll bars contribute to a cleaner and less cluttered appearance, which is in line with current design trends that emphasize minimalism."

Good, let's all eat roach powder...it's minimalism too. Makes you think voting and what companies you buy from matter.

That's not an improvement because it was there already, since 1996 and the first mouse with a scroll wheel. You don't use computers do you.

What's handy is being able to scroll a large document to a specific part very fast. I encourage you to try to use a mouse wheel to scroll through an entire PDF book with hundreds of pages, and watch you throw your computer out the window because it is too slow and frustrating.

The biggest recent improvement (which the narrow or hidden scrollbars destroy) is some programs like chrome and matlab mark the location of a searched word on the scroll bar with a thin line, so you can instantly see how many and where they are in a document and immediately scroll to that location.

"No need to hunt for a scroll bar"

How is it a need when you have a mouse with a wheel that scrolls the page no matter what the scrollbar looks like?

Before there was no need. With disappearing or narrower scrollbars, there is a need.

Now, there's even more hunting and worse, confusion. Now you spend far more time scrolling, get repetitive strain injury, carpal tunnel syndrome and increase eye strain hunting and positioning the mouse when you need to scroll in a large document. Disappearing scrollbars make it even worse because you're not sure where to move the mouse to make it appear.

Also I have beginning stages of Parkinson.. So my hands shake really bad.

I have changed the registry and I have larger scroll bars. But try to open file explorer or a system owned file and they are skinny..

"Windows 11 aims to provide a sleek and modern user interface. Narrower scroll bars contribute to a cleaner and less cluttered appearance, which is in line with current design trends that emphasize minimalism."

And, yet, Microsoft decided to make the task bar so big that it's practically screaming at you and added some stupid ribbon to the file explorer that you can't get rid of. A ribbon, I might add, that has tools that literally everyone uses keyboard shortcuts to achieve.

I call bs on the notion that MS is going for "minimalism" and instead continues to ignore its users and do whatever it wants.