Practical reasons include fighting with a lightsaber dude. I swear jedi chose this outfit solely because they could use the force to stop it from bunching in multiple locations, slipping or knocking shit over. It also must become made of science fiction materials that have you not pass out from heatstroke or freezing to death by degrees.

Like it's not the least practical convention wear I've ever had since "being able to easily fit through a single door" has tripped me up before... But that doesn't mean it's good everyday wear.