Among the many historical inaccuracies that comes with RPGs and the galaxy around them, one that really bothers me is the shield wearing with plate armours. That's just something that didn't happen. Well, outside joust, but in jousts shield where more of a designed target than a protection. The introdution of plate armors simply made shields reduntant and obsolete because they where just this good as armours. There was no need of shields and it was way more appealling to hold a weapon with 2 hands hoping to strike hard enough to get through plates or to just crush the bones underneat. The problem is people think that every armour was 'medieval', but plate armours are a very late technology, as late at the XV century, so much that they had to be soon redesigned to be bullet proof on a chest, since firearms were getting common already.
I think you need to do a LITTLE more research there mate.
You fell into a very common trap for people learning from Youtube historians: You get only part of the picture, since they themselves are not fully knowledgeable. (not saying YOU learned from Youtube, it's just very common nowadays)
Plenty of examples of full plate wearing, shield using fighters in set battles. (Granted it was not a common thing in EUROPE, but full armour isn't a European only thing). It's even a fact that the shields (some, in some places) got thicker in tandem with the armour. What you're stating as "a well known fact" is actually a well known misinterpretation by many scholars. Which happens when you confuse correlation with causation. And generalise worldwide usage from a smaller sample.
That said, in Europe (seeing as the armour you react to are of a "European style" 'ish) the development of better armour (up until firearms were more common when it reversed again and shields actually became more common again for a time) DID mean shield usage of said full plated armour equipped battle troops were less and less common, due to the need for using 2 handed weapons, such as mainly polearms. And the shield would hinder more than it would be of help. More cons than pros as it were.
Very common inaccuracy that really bothers me, in fact. The "not whole picture, state parts as absolute total fact" inaccuracy.
