The builtin scanner in macOS allows either previewing, or scanning into a file, but it can't save the preview into a file. Previwing is crucial in order to determine what to crop or rotate, but scanning another time after the preview wastes a lot of time.
The builtin scanner can rotate, but it can't preview the rotation. It has limited color correction capability (which is important for making black & white documents... more black & white, and well-readable). It can't save to multi page PDF. It can't tweak JPEG quality. It can't preview in color but save in black & white.
And OCR. Damn, so nice. It can generate PDFs with selectable and searchable text!
VueScan can do all of that. Strongly recommended if you need to scan more than a few pages on a regular basis. Well worth the price tag.
The only downside is that its UI is a bit complicated, with lots of settings. It should be regarded a power user tool.
When I buy furniture or another appliance, I throw away the paper manual and store the digitally scanned version. It's hard to find paper documents: there are too many. In comparison, finding digital documents is trivial.