In 3 phase induction motor,why do you need three phase and not use neutral in induction motor,detail me?

Because in 3 phase system 3rd phase provide return path that neutral provide in single phase.

Three phase motors are normally delta connected in order to produce higher torque. So there is no neutral.

Incase of star connected motor, the load is balanced and so there is no need to connect the neutral point of motor with supply neutral.

three phase motor are use in industries and this connection is star delta.neutral is star connection