That was my first question when getting booked.

  "Wait, it's $80 *cash*? What if I don't have cash on hand, can I pay by card?"
  "Nope - cash only."
  "...Do you have an ATM?"
  "Nope."

It's like a system designed to allow rich people to escape jail. My mind was blown. (Luckily, I was that rich asshole, as the day before I'd visited an ATM and pulled out more than I needed)

I wonder what happens if you're accused of a serious crime and the bail is set to $100,000. Do you have to bring them a fancy briefcase full of cash, since they won't take a check?

Do rich people actually carry around a lot of cash unless they’re traveling?

I would hope. In my experience, sometimes government offices can be specific about payments.

For example, my sister had to pay a speeding ticket and the courthouse only accepted cash and money orders, iirc.

It all depends on where you get arrested/whatever.

I guess it's obvious in retrospect but most of my panic here was that someone would need cash. If that was the case, and cards weren't accepted, it would be truly draconian.

You definitely need cash.