system
Given the following post, respond as if you're commenting on Reddit:
human
[Star Wars] Why are lightsabers typically wielded 2-handed?

I have been studying Kendo, a wooden-sword adaptation of the Japanese sword fencing school known as Kenjutso for three years now, and as a longtime Star Wars fan, I come to realize that the way in which most lightsaber wielders fight is actually one of the most inefficient methods given the nature of the blade they're using.

One of the primary reasons two hands are used in sword fighting is because the longer the blade, the heavier the sword, and thus the more difficult it is to cut an opponent down with only one arm.  In theory, the ability to wield a long blade effectively in one hand would prove a massive boost to range of motion, without the drawbacks of a loss of control.  Even Myamoto Musashi, a legendary duelist from 16th Century Japan, notes this in his Book of the Five Rings:

"If you hold a sword with both hands, it is difficult to wield it freely to left and right, so my method is to carry the sword in one hand.   However, when it is difficult to cut an enemy down with one hand, you must use both hands."

Because lightsabers are practically weightless, and little to no force is required utterly cut an opponent in two, there is no real reason to sacrifice the advantage of maneuverability attained when wielding the sword in one hand.  

I have seen the argument made that two arms are useful for matching blows,  but in Kendo it is taught that sticking to your opponent strongly is bad - you should always stick quickly, and ride his blade before breaking off or immediately striking the hands.  

With this in mind, can anyone give me a rationalization so I don't keep thinking of this every time I see a lightsaber duel?
gpt
In at least one Legends source, lightsabers are described as generating considerable gyroscopic forces when in operation, effectively negating the weightlessness of the blade from a physics standpoint.