Because I don't believe a proper history source would feed you that kind of crap.
Because plate armor is completely invulnerable against arrow fire? No. Pick up a book, I personally recommend something about the Hundred Years' War or
Why the English Had Such an Early Advantage Against Bumblefuck Tincan CavalryOne can't argue for historical accuracies in this game because there is no set time-line, or historical model for that matter, to follow. While bows played a pivotal role in a great deal of medieval combat, eventually blacksmiths were able to discover formulas to make plate armor very resistant, as seen in the video Nemeth posted. Times change, equipment changes.
Ultimately it all comes down to reference. Could the bow pierce plate armor? Up to a certain era of time, yes; but as times and technology advanced, armor was made very powerful while the construction of the bow remained pretty much the same. It's what led to the discontinued use of the bow and the invention of guns and other pretty things that were capable of rending steel and flesh alike, while sometimes meshing the two materials into a very fun slurry.