Starter is used to reduce starting current.starting current 
is usually large because of inertia,charecteristics of 
motor winding(at starting slip=1,rotor resistance low 
implies less  back emf).So at starting we use starter .for 
example.STAR DELTA starter.by using a starter at least the 
switching is improved which is much important for safe and 
longer life time use.simply a DOL can be used for lower 
rated motors (up to 07 HP)in this case.for higher rated 
motors (up to 15 HP)we can use a star delta connection.a 
delta connected motor takes 1.7 times line current than a 
star connectd motor.think ! at starting the current is 
almost halved .Now a days we use drives (power electronics 
products which not only takes care of starting of a motor
(improving power factor) also controls it as perrequirement.