If the step is made with the body moving as a unit from the center, it can protect you from sweeps and throws and power upper body motions. Leaning back while moving invites attackers to run you over and leaning forward invites them to throw you or attack your face. Uechi Ryu turns also involve firmly planted feet. One planted foot drives the motion of the other leg, so if you are attacked while you are turning, you are less likely to be thrown off balance. Second, as you complete the turn, drive your body directly sideways so your rear leg has become your front leg.
Turns can be powerful as well.
A wrist-lock driven by a turn is a powerful throw, and the last motion in Kanshiwa Bankai is a 90 degree turn which snaps an enemy's elbow without requiring any arm movement.