Sometimes the company will need to increase the volume that a production plant delivers, since maybe it is not running at full capacity. An example of this would be a food manufacturer of tinned soup that has a factory which can operate 24/7, designing different derivatives of the soup in order to lower the unit cost of production. So product lines are extended, in this case the reason being is to ease operational efficiency.
Intense competitive rivalry in the market will also lead to the need for NPD. Just think about your smart phone and how quickly such products go through their product life cycles, throughout your customer life-cycle.