I think the point is that people were breeding rats so that they could make more money. Then when the ended the 'program', the rats just got released, making the problem worse, no?

It's a matter of the payoff though. Sure, it's easier to cut the tail off a single dead rat than a single live rat.

But if your goal is to maximize the number of rat tails you end up with, cutting it off a live rat is probably worth the additional effort.

You can breed a living, tailless rat to produce more rats.