How come no sith/jedi I'd imagine sith more doing it just wildly swing their lightsabers like a maniac(of course not cutting themselves) but wouldnt it be fullproof? I mean not many people would likely survive someone with more than one lightsaber wildly flailing their arms

Grievous did it.

Cause swinging wildly like a mad man does not generate a force field.

it's also using a tremendous amount of energy in useless swings...if someone is half-way decent at mounting a defense, the tide of the fight will quickly turn to them as the person swinging about wildly like a madman starts to wear themselves down.

 

just using a sword requires very little power to do harm to a person, and a sword made of pure energy probably even less so. it's more about control and establishing counter-attacks with quickness and precision over power.

 

in traditional fencing, even the "overwhleming" attack styles are often still very coordinated, they may seem wild to untrained eye, but require a lot of skill to pull off. also, you dont want to end up swinging yourself into a vulnerable position by just flailing about.

A lightsaber projects a 'beam' of plasma. It has no weight to it, save the weight of the hilt. The reason only jedi really use the things is because of how ungainly they are. It'd be like trying to fight with a flashlight. But when you hit another saber, or a blaster bolt, there is still the impact. Without the weight of the blade to counteract the force of the blow, the saber would rebound, wildly.

 

Jedi/Sith/People-with-the-Force have the instincts and the raw ability to fight in this manner. 'Flailingly madly' with a beam of plasma would only place you, and any allies nearby, in danger.

 

I take it you've never been through any sort of Martial Arts? Or sparred in some way? I've taken some Kendo, and am a part of a medieval society that has a combat aspect to it. 'Flailingly Madly' is reffered to as Cluba-seal. To anyone who has been doing it long enough, your wild flailings are giant, gaping holes. You cannot spin fast enough, nor move fast enough, to cover every inch of yourself. With a lightsaber, all it takes is a brush, a touch, and that is a limb gone. Any force user trained in combat would tear apart an untrained initiate, particularly one versed in the 'windmill' form.

The same reason people with real swords don't fight that way.

 

Also the same reason professional hockey teams don't just hire a really fat sumo wrestler to lie down in the goal net.