From those races I’ve tested, Vulpera, Gnome and Mechagnome (females) have quiet a few fight vocalizations–more so than other races I’ve tried that are darn near silent: HMT, Orc and Velf (all female); so if you’ve not tried a Vulpera, Gnome and/or Mechagnome for the monk class, give it a go, 'cause they be noisy! LOL
True; but, then, it’s perplexing the Blizz has some races fight nearly in silence as monks, while others vocalize for nearly every spell. It’s a strange inconsistency, IMO.
I suppose you’ve got a point. Monks in general tend to lose people’s interest because of the Far East themes juxtaposed against mideaval fantasy. Although plenty of people are interested in bare knuckle brawlers, not necessarily a martial arts expert.
Returning to the point of the OP, I would point out that students in irl martial arts are expected to bellow and shout with each strike. For one as noted above it adds more power. A second reason is it is more intimidating to an opponent. So a loud monk would be closer to an actual martial artist (never mind the leg sweep that resembles some sort of crazy helicopter kick).