Seems like it was more of an artistic choice than any sort of technical limitation or "being lazy." Tails poke through other one piece outfits so I see no reason the same couldn't be done here if they wanted to.

Whether that choice was good or bad would be in the eye of the beholder. If one tailed race player wants the tail to show and another prefers it gone, who is correct? Ideally the solution would be to give everyone the choice between the two but unfortunately there is no /tail feature at the moment.