Is it just so bike assembly is easier to do in two parts, ie. fitting the bars later?
Mainly this and means you can ship them without committing to which lever does which brake or being too fussy with hose length. If you're happy with the set up you'll not really missing out on anything replacing the hoses without them, bit of a PITA for not much gain though.
I wouldn't be doing it just for the sake of doing it, but if we replace her levers or something in the future, I want to remove the splitters if they provide no benefit.
Mainly this and means you can ship them without committing to which lever does which brake or being too fussy with hose length. If you're happy with the set up you'll not really missing out on anything replacing the hoses without them, bit of a PITA for not much gain though.