This is from Reddit, not my own words.
"When you get into armed martial arts (especially something developed for agility and speed) like WuShu or the various Shao Lin Kung Fu forms, one of your major strategies is to go blade to blade, because your opponent will be using their similar speed and agility (swinging from cables non withstanding) to block In a way that enables them to instantly counter attack agressively. You go blade to blade in a very practiced routine to try to work your opponent's blade into a position to attack, without the counter attack. Also to work your opponents center of gravity over their heels.
If you do that you throw off their center of balance, and this takes away some of your opponent's agility and strength, because they have to use those resources to keep their feet. Especially if two opponents know each other and each others combat styles strengths and weaknesses, even in a competitive environment it can look choreographed.
So those kinds of scenes actually fit the prequels quite well.
In the originals we have a different situation. Yoda and Obi-Wan are teaching Luke to be a weapon, not a martial artist. Kind of like the difference between Bruce Lee (absolutely a lethal guy) and a samurai warrior. In fact the sword master hired for the originals based lightsaber combat on single katana combat. It's more direct and designed for single hit kill. Extremely fast but very aggressive and linear moving.
Both kinds of fighting, martial arts and combat, are just as lethal but they're very different.
This kind of combat fits Obi-Wan, Vader and Luke very well. Vader is wearing heavy (Saber resistant) armor. Obi-Wan is not only older and less agile (the force could make up for that though) but Vader is a very different opponent now, and his strategy is to survive long enough for Luke to witness his sacrifice. Now he needs to stop each potentially lethal attack as they happen. Luke is almost on a suicide mission against a titan, and needs to get the upper hand fast. He needs to win at Street Fighter, not chess. Two hand Katana fits these movies with these characters perfectly.
It also makes sense because it keeps the blade in a very tight controlled area, with most of the moves keeping your own blade (made out of magnetically contained plasma) as far from you as possible for most of the fight.
So now we have TFA. Kylo Ren is using what essentially boils down to a German or Scottish bastard sword. I used to do SCA tournament combat, and what Ren is doing looks very similar to 11th or 12th century German. He has a lot of flourish though. It's for camera so there's going to be telegraphing. European medieval combat was both for duels and for on field warfare, and this is where we find Ren. Vader comes to a battle, leads and single targets. Ren leads and is in the middle of the battle.
Fin is opportunistically striking, he's not a highly trained martial combatant, and Rey is an efficient street brawler. She only gains an upper hand by calming herself into the force and using its potential.
All of these styles were chosen for their era in the Star Wars timeline and fit very well."