They actually did reply to this question before. They said that since some job emotes target other players (SMN, RNG, DRK, WHM...), it would be all too easy to be targeted for harassment by players spamming those emotes on you. If "motion" subcommand was available, people could spam you with those emotes and harass you without you being able to report them because you would be unable to see their name (and in crowded places, it can be hard to see someone doing the motion).