Of course we're worried about the common man -- the same reason why you don't give a teenager the Jehovah's Witness translation of the Bible and even more so in the days before the internet, before freely available books when one mistranslated Bible could wreak havoc -- what if someone say wrote "oath's" instead of "oaths'"? It gives a subtle change in meaning, right?
"In 1466, before Martin Luther was even born, the Mentel Bible, a High-German vernacular Bible was printed at Strassburg. This edition was based on a no-longer-existing fourteenth-century manuscript translation of the Vulgate from the area of Nuremberg. Until 1518, it was reprinted at least 13 times." -- yes, this is proof the the Church was ok with books translated into the vernacular - if it was properly vetted. What was wrong with Luther's? Well, the addition of the word alone to Romans 1:17 is a good example of how one can build up philosophy from a wrong translation
Granted, this was not as bad as the wholescale mistranslation of the Jehovah's witnesses or Gnostics etc.
Salvation is by faith ‘alone’, without works (Eph.2:8-9, Tit.3:5), so it is all of grace.
And if it is by grace, then is it no more of works: otherwise grace is no more grace. But if it be of works, then is it no more of grace, otherwise work is no more work’(Rom.11:6)