No clue why the kick function isn't in the game but then again, it not being in the game also prevents parties of three to vote kick the one random that they are running together with when they reach the end of a dungeon or boss fight. Then theirs the in-ability to tell someone or talk to your linkshell and FC could be due to going into dungeons with players from other servers as well or its a way to keep players from getting distracted during dungeon runs.