> In this case, the financial penalties imposed on the companies themselves seem like a more effective tool.

Why do you say that? Depending on their size, financial penalties can be seen merely as "a cost of doing business."

The ultimate goal here is to hold car makers accountable for their systematic fraud and violation of emissions standards. Accountability will deter future violators.

There's no better way to convince "golden-parachute" executives to take these transgressions seriously than to put violators in jail.