You must have observed that there is a rating mentioned on every motor like....some...KW
Whenever a motor is connected in delta, it offers a power equal to this rating.
Whereas, when the motor windings are connected in star, the power offered is much less than this rating.
Power=(KW rating)/3
Also, you know that torque is proportional to power.
So, in order to use a motor optimally, we connect the windings in delta.
However, there is a large amount of current when the motor starts, so in order to keep these windings from burning out, it is preferred that initially the motor should be star configured( current divides in star configuration,right!) and after gaining momentum, it should switch to delta configuration.
P.S:
It is not mandatory to use delta configuration in motor. Star configuration can also be used, but the problem is that you'll not like a motor that runs slow and stops or burns it's windings whenever a heavy load is encountered, right??
Hence, star configuration loses the race with delta configured motor in terms of the power offered, torque, speed and the heavy load handling capacity of these two.
