There's no reason why there shouldn't be both sprites available.
Actually, there is a reason.
The game system is built around tying sprite to class with only only variable that the client understands for alternating it beyond that, being male or female. Adding some sort of _alt sprite would require re-engineering the server code that refers to the job or gender probably, and re-engineering how the client interprets which sprite to display.
Bottom line: requires coding and client testing so that it doesn't b0rk people when the new client is released.
The game's client and server software framework is like 10 years old and I doubt any of the original coders are onboard.
More than likely kRO determined this would be too much work for something that is tantamount to a niche & unimportant aesthetic change; particularly in the face of all the demand their coders currently have for bugfixed and class balancing.