Beauty is in the eye of the beholder; people perceive the same thing in different ways, which is why eyewitness testimony is so unreliable. People also tend see what they want to see. Ancient two-dimensional images on temple, vases, etc. (depicted in a flat “South Park” style) of two warriors facing each other with their arms up may be perceived as two friends about to hug, two dancers, two happy soldiers, or two opponents ready to fight. Since some of the images appear to be have vertical fists, some vertical punches see these images as proof that vertical punching had ancient roots, not that it was simply the way the artist depicted hands. Some modern sculptors find it difficult to sculpt realistic looking hands, so they hide the hands of their statues behind something. Some future civilization may unearth these sculptures and conclude that people of our time did not have hands, or had deformed hands that we always hid.
When it applies to the martial arts, I always say, “If it works for you, then use it.” I once had a student who performed a round/roundhouse kick without ever turning his support foot. While I usually train people to rotate the support foot to add power to the kick, since he could bend a punching bag in half with the kick, I did not bother to correct his technique; it was obvious he did not need to rotate his foot. While the benefits of horizontal punching far outnumber and benefits of vertical punching, I would not try to convert a vertical puncher who was effective at vertical punching. While I primarily teach new students how to use their natural horizontal punch more effectively and efficiently, after they become proficient at horizontal punching, I will also show them the vertical punch, since there may be an occasion to use it.