Yes, you have to counterbalance against the need to make the voice distinctive and characteristic, but that's true of everything else as well. True, you can get away with an intentionally pellucid prose that draws no attention to its character -- even in first-person and omniscient -- and characters need more personality, so there's more limits to how you can stylize your dialog, but that doesn't make style off-limits.
For one thing, it helps characterize. Most style tips will make dialog more vigorous and straightforward, which makes your characters stronger and more determined.
(And if you complain such characters are not realistic, there's the door. Outside it, you will find Real Life, in which not only dialog but everything is done with a consummate level of realism, twenty-four hours a day, straight. The only good reason for fiction is to do something that Real Life ain't got, and realism ain't it. If you still want realism, don't let the door hit you on the way out.)
For another, it sharpens conflict. Not only will it make the hero and villain stronger, but when they are arguing, their opposition will come more clearly into focus when it is expressed as powerfully as possible.
For a third, it just sounds nicer. Which is always an advantage. And whether it's transparent prose that never trips up the reader or a distinctive voice that the reader will read on to hear more of, it's an additional attraction.