REGISTER TO REMOVE ADS
Because that was an internal fight within Sora over who should be in control, basically.
Roxas wanted to know whether or not Sora was worthy of being the one in control. He didn't want his sacrifice to be worthless. So, he engaged him in a fight.
All within Sora's mind, of course.
It was kind of what Xemnas did in that fight
with Sora at the Memory Skyscraper illusion.
lol What? Neither of those make any sense at all. Do you understand what those terms mean at all?
Back on topic:
I thought the fight scene was one of the better scenes in the whole game.