[thedjinn]

Most people probably don't even refer to the macOS versions by number but by codename.

[gregoriol]

Sure, but version names are hard to order: was Catalina before or after X? who will remember? (maybe if it at least was like Ubuntu with names following alphabetic order)

[saagarjha]

Nit: Big Sur is a marketing name, not a codename. Apple has their own names for this things ;)