> would likely create prisons to protect the people How would prisons protect people? By deterring the people who might endanger them, by removing the capacity

> would likely create prisons to protect the people How would prisons protect people? By deterring the people who might endanger them, by removing the capacity of people who do cause harm to cause more harm, by punishing those people, and by rehabilitating them into society. The reasons aren't secondary or primary. They're different sides of the same coin, just stated from different perspectives: how to deal with the problem of crime vs. how to protect society from criminals.