IIRC, originally the names were code names for internal use only. It seems after Microsoft started using names instead of years, Apple started aping them. Since Microsoft has stopped using names and now just uses numbers, Apple’s aping is outdated and should be dropped.
As an aside, I always thought that the LAST big cat name should have been Smilodon and used for MacOS 10.10. Additionally, there should never have been MacOS 10.11 through 10.15; they should have just been MacOS 11 through 15 and “Sonoma” should be MacOS 19.
Named macOS versions make it a lot easier to Google for information relating to that release. Except, of course, if you’re searching for information on Leopard, Lion, or Sierra.
But besides that point, I don’t buy your premise.
The first OS X version to lean into using the internal code name for marketing was OS X 10.2 Jaguar, in 2002.
Windows before 2002 was Windows 1-3, NT, 95, 98, 98 SE, 2000, ME, and XP. None of these were code names, they were the actual branding. They all had different code names. Windows 95 was “Chicago”, but they never marketed it that way. Windows 98 was Memphis. Windows XP had a bunch of code names. Vista was “Longhorn”.