idk because he wants too lol, and there are different styles, think of it like a knight and samurai, sure they both use swords but they fight completely different. A knight will use more strength behind his blows, where a samurai will use more speed. That's how it is with the different lightsaber styles. The user's skill does have alot of influence on the fight, but the style can make alot of difference in a even fight.
In the original trilogy you dont see the styles really because everyone fights the same. In the prequels you see them more, like Dooku has more of a fencer style, and Yoda is a flippy fast style, Anakin is an aggressive powerful style and Obi wan has more a a defensive style.