Having a shipped a Windows filesystem driver, I can tell you that Windows's lowest level filesystem APIs "you buffer/stream rather than allocate, you pass point

Having a shipped a Windows filesystem driver, I can tell you that Windows's lowest level filesystem APIs "you buffer/stream rather than allocate, you pass pointers rather than copying data, you use indexes/hashes for lookups rather than full scans, and so forth" Memory was a lot more limited when those APIs were designed! Then again, many programming languages expose simplified APIs for the exact reasons you describe. It's a lot easier to encapsulate all of the above when all you care about is getting an array of filenames in a directory, and then performing your own application logic to filter it further.