Final answer:
The author included the detail about rules against killing rabbits to show the problems rabbits created for farmers.
Step-by-step explanation:
The most likely reason why the author included the detail about rules against killing rabbits in the text is to show the problems rabbits created for farmers. By highlighting these rules, the author is indicating that rabbits were causing issues in agricultural settings, possibly by damaging crops or competing for resources. This detail helps to emphasize the negative impact rabbits had on the farmers' livelihoods.