Because that looks intimidating but doesn't have control or effect? Because the number of truly ambidextrous people in the world is seemingly lower than 1%? Because it's really hard enough to get the right number of spins for the distance when you throw a knife with your dominant hand and nothing disrupting your balance? So sad I've never seen a throwing dagger(from those magic bags of holding) hit hilt first, lol.
Yes, it's super cool looking in anime to be slicing and dicing with both hands independently running straight through armies, but someone with a sword breaker or a main gauche as secondary weapon was using a very different style of fighting than that. I don't mean to rain poop on the parade, and THIS IS A GAME, but I don't want it to be some naruto game or whatever. I admit, IRL intimidation factor is a great thing for your weapons to have, but kind of hard to use intimidation on bots. Also, IRL you don't want to take ANY hits so would be more a tactic of trying to tie up your opponents weapon with one of yours and then...
It's a neat way to fight, some people actually did it, and games should be fun, so yeah why not have a form of dual wielding? As long as it's not the "whirlwind of death" overpowered cartoon stuff(which was fine in Max Payne or Lord of the Rings) which doesn't fit a semi-realistic/historical setting. It would make some sense to me if dual wielding involved really HEAVY skill/proficiency and maybe even attribute investment to develop. If you want to invest the years to become a blades master instead of a leader of men or whatever else, that should be your option in a wide open game, sure. Work your way up perhaps, being proficient with one dagger size weapon defensively in your off hand to gain strength and/or speed in your non-dominant hand, learn to get into a weapon bind and maybe eventually get to the point of flurries of strikes if it's not too OP for the bots. Im not saying it might not be fun to turn the damage down to easy add bullet time and dual-weilding cyclone of doom skill-thats just not M&B.
For all the enthusiasts go find two sticks and play a bit, notice each time you smack yourself or your weapons by accident. Consider if you just hit yourself in the face with a sword instead of a stick....
Personally I'd rather have left handed warriors in the world first.