Who told you they are th academic standard? For starters, their translations are relatively recent.
Joseph Frank himself often referred to Garnett on the basis that is was the most widely accessible to English Speakers, and McDuff, Avsey, Wilks, Meyers, etc all produced translations either before or contemporaneously with P&V, and frankly are more stilted.
I have two books at hand here, a Bantam Classic "Eternal Husband and other stories" by Pevear and Volokhonsky and "Gambler and other stories" by Ronald Meyer. Let's compare:
A Nasty Anecdote (P&V)
>This nasty anecdote occurred precisely at the time when, with such irrepressible force and such touchingly naive enthusiasm, the regeneration of our dear fatherland began, and its valiant sons were all striving toward new destinies and hopes.
A Nasty Business (Meyer)
>This nasty business took place just at the time when the renaissance of our beloved fatherland was beginning with such irrepressible force and with such touchingly naive fervour, when all its valiant sons were seeking new destinies and hopes.
Now at least, this should highlight that in translation, there is actually little substance lost, and it is largely a matter of form. But as you should be able to see, P&V have a weird grammatical syntax that comes across as stilted to the natural English speaker, without being any more elucidating.
I have read some of their other works and they are clearly clouded by some kind of mission for accuracy, yet fail to render some sentences in a comprehensible manner in English (The Adolescent was a big one for this - EveryMan's Library), where I found myself laughing at the poor chose of words that take you right out of the text.