Rotor Constructing of Squirrel Cage Induction Motor

If the bars are axially parallel, there might be small jumps (cogging) as the rotor advances from one bar to the next. A slight twist can allow one bar to fair more smoothly into the next, with a bit of overlap. That's a qualitative layperson's view.

Yes ,aluminium /copper rod in the rotor of sq.induction motor is not straight ,due to magnetic locking i.e.coogging .If rod is straight w.r.t. stator slot then ,it may be rod south polarity w.r.t.nearest slot having north pole.then magnetic locking may created between them.max'm starting torque will not created.

It also gives better starting torque.

And maximum starting torque in every position between rotor and stator . I heard that old motor with straight line between rotor and stator slots had bad and loud sound also .