Let's say that you are a doctor and you live in a town of 20,000 people with one hospital. You are stuck being "loyal" to that hospital unless you move. Now let's say that you live in a metropolis of 2 million people and multiple hospitals. That gives you the option to move between jobs if they become available.
My impression is that cities and towns used to be smaller in the past and commuter culture wasn't as popular as it is now.
I'm ok looking at the past with rose-tinted glasses, but context is also needed to understand the decisions that people made back then.