Tide laundry detergent maintains the same market share it had 50 years ago because of the sales contributions from its various line extensions.

Tide laundry detergent maintains the same market share it had 50 years ago because of the sales contributions from its various line extensions. It can be said that Tide employs a preemptive cannibalization strategy in generating line extensions. What does this mean? Why do they choose to use this strategy?