[Armisael]

Even if armour had some sort of exclusive blaster damage filter, which it doesn't, not everyone wears it. It is pretty silly for there to be so many swords around in this era. I think that in Star Wars generally, sword use was always primarily the domain of Jedi knights (and certain primitive cultures). But it's really just a game design choice, the same way each and every sword, knife and fork is supposedly made out of cortosis -- so that those nifty battle animations don't seem quite as ridiculous as a regular steel sword parrying a lightsaber.