Initially, because the early Mac OS X Finder was a bad enough set of compromises and slow as molasses without adding database lookups to another part of the fil

Initially, because the early Mac OS X Finder was a bad enough set of compromises and slow as molasses without adding database lookups to another part of the file system (at a time when HDDs were universally spinning rust and iBooks and PowerBooks often trucked along with 4200rpm drives). The .DS_Store files could be there already in the directory and hidden from users with a flag while Apple figured out whether UFS or HFS+ was their future file system. Now? Well I/O performance is hardly a consideration for the latest Macs, but they’re there and they work, except the Mac OS X Finder 20 years later while far better than it’s debut performance is still a load of crap so it can still forget your custom view settings for a directory.