IIRC Knights used Poleaxes and Halfswording when plate armour came into play.
Why mess around with a sword that bounces, When you can pierce through, or use the Axe as a hammer, or tackle your opponent to get him to the ground? Halfswording is a working technique but en-masse it's much easier to use something else.
Swords are overrated, overgloried stuff thanks to popular culture.
Massive swords are for the elite knights, spears are for the lowly peasants. Which weapon do you think most people would chose?
Sure, only nobles had rights to wear such weapons, but most of the time it was only a status symbol.
They picked something else for a fight, unless they had to fight peasants.
I'd pick something else than a sword if I'd have the fighting knowledge, against a fully plated opponent.
Just my 2cents though, that's what I think. Why all the trouble with a sword, if you can just whack somebody to death?
Swords can also cut through metal armor with ease. I learned that from Hollywood. There is no reason to not use one!
lol