The only thing I can think of is that some clients might want raw keyboard events. It does seem to me (an outsider) like Keysyms are the better level of abstra

The only thing I can think of is that some clients might want raw keyboard events. It does seem to me (an outsider) like Keysyms are the better level of abstraction for input for the overwhelming majority cases, and the translation should happen as early as possible in the server, and that's even before ignoring things like the asynchronous nature of xlib making keyboard remapping &c. unreliable for sending key events outside of the primary keymap.